P0300 & P219A codes

[asilverblazer]

To me it sounds like cylinders the truck is leaning out some cylinders too much. When you "floor it" the miss fires go away. The ECM doing a 'power enrichment' dumping extra fuel in.

 

That makes me think those cylinders aren't getting the amount of fuel they should. Either the O2 sensors are seeing too much unburnt fuel and leaning it out too much or the injectors aren't shooting enough in. I don't think it is an O2 sensor issue because that would cause a problem on all cylinders.

 

Conversely, the amount of air entering the cylinders could be unexpected and the fuel trims are trying to correct it. For it to only be on a couple cylinders it would have to be intake gaskets or valves. 

[ktuck]

On 4/30/2024 at 1:19 PM, asilverblazer said:

To me it sounds like cylinders the truck is leaning out some cylinders too much. When you "floor it" the miss fires go away. The ECM doing a 'power enrichment' dumping extra fuel in.

 

That makes me think those cylinders aren't getting the amount of fuel they should. Either the O2 sensors are seeing too much unburnt fuel and leaning it out too much or the injectors aren't shooting enough in. I don't think it is an O2 sensor issue because that would cause a problem on all cylinders.

 

Conversely, the amount of air entering the cylinders could be unexpected and the fuel trims are trying to correct it. For it to only be on a couple cylinders it would have to be intake gaskets or valves. 

You make some logical and valid points, I think, especially about the amount of fuel in the cylinders. The spark plugs reflect a lean condition and the extremely high negative fuel trims give reason to see where the fuel amount has been cut drastically. I'm wondering if some sensor(s) are fooling the ECM into thinking there is too much fuel when there really isn't. There are two cylinders missing consistently but others are missing too, just to a much lesser extent. I was curious about the overall misfires so I separated the historical misfires by banks. Bank 2 has 6992 and bank 1 has 5752, so each bank has a similar share of misfires. Individually #2 has 6859, #5 has 4188, and #7 has 948. The rest of them range from as few as 14 to around 400. One shop I had diagnosing the issue said collapsed lifters were the likely cause. Interestingly, the total misfires from the AFM cylinders is 1479, while the total misfires from the non-AFM cylinders are 11,265. I don't believe collapsed lifters are the problem. But there could still be a problem with the valves as you mentioned. I think I can rule out intake gaskets as I've had the intake off twice and the gaskets on cylinders 2 and 5 were perfect. And if I had boogered up the gaskets, how likely would it be I would mess up the exact same cylinders each time...I'm not that skilled!

[asilverblazer]

13 hours ago, ktuck said:

You make some logical and valid points, I think, especially about the amount of fuel in the cylinders. The spark plugs reflect a lean condition and the extremely high negative fuel trims give reason to see where the fuel amount has been cut drastically. I'm wondering if some sensor(s) are fooling the ECM into thinking there is too much fuel when there really isn't... I think I can rule out intake gaskets as I've had the intake off twice and the gaskets on cylinders 2 and 5 were perfect. And if I had boogered up the gaskets, how likely would it be I would mess up the exact same cylinders each time...I'm not that skilled!

Perhaps its the opposite then - all the others cylinders are getting too much fuel, then the O2 sensors are picking it up and leaning them all out. Essentially an injector balance issue. Because 2 and 5 are flowing the least amount of fuel, when their respective bank gets leaned out because all the other injectors on the bank are flowing too much it causes a miss fire in the leanest of the injectors. 

 

What would happen if injector for 2 was swapped with 3 so that the two miss firing injectors are on the same bank? I would expect the two banks to have significantly different fuel trims then. This would also confirm it is in fact a fueling issue. 

 

It could also be a different type of valve train issue not associated with a collapsed lifter. 

 

Has a compression check been performed?

[asilverblazer]

Diagnostic Aids

• The fuel trim cylinder balance diagnostic is very sensitive to heated oxygen sensor (HO2S) design. A non-OE sensor or an incorrect part number may cause a DTC to set.
• Monitoring the misfire current counters, or misfire graph, may help to isolate the cylinder that is causing the condition.
• Certain aftermarket air filters may cause a DTC to set.
• Certain aftermarket air induction systems or modifications to the air induction system may cause a DTC to set.
• Certain aftermarket exhaust system components may cause a DTC to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

 

Component Connector End Views

Component View Reference

 

Powertrain Component Views

Electrical Information Reference

• Circuit Testing
• Troubleshooting with a Test Lamp
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Connector Repairs

DTC Type Reference

 

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

 

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON.
2. Verify no other DTCs are set.
   • If any other DTCs are set
     Refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
    
   • If no other DTCs are set
   
   
3. Verify DTC P219A or P219B is not set.
   • If a DTC is set
     Refer to Circuit/System Testing.
    
   • If no DTC is set
   
   
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records data.
5. Verify DTC P219A or P219B is not set.
   • If a DTC is set
     Refer to Circuit/System Testing.
    
   • If no DTC is set
   
   
6. All OK.

Circuit/System Testing

1. Engine idling, transmission in Park or Neutral, verify the manifold absolute pressure (MAP) sensor parameter is between 19–42 kPa (2.7–6 PSI).
   • If not within the specified range.
     Refer to DTC P0106.
    
   • If within the specified range, inspect for the conditions listed below:
    
   • Modified, damaged, leaking, or restricted air induction system components.
   • Improper operation of the crankcase ventilation system. Refer to Crankcase Ventilation System Inspection/Diagnosis.
   • Split, kinked, or improperly connected vacuum hoses.
   • Restricted, damaged, leaking, or modified exhaust system from the catalytic converter forward. Refer to Symptoms - Engine Exhaust.
   • Malfunctioning fuel injectors. Refer to Fuel Injector Diagnosis.
   • Fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
   • Excessive fuel in the crankcase due to leaking injectors. Change engine oil as necessary.
   • Malfunctioning ignition system. Refer to Electronic Ignition System Diagnosis.
    
   • If a condition is found
     Repair as necessary.
    
   • If no condition is found
   
   
2. Test the engine for any mechanical conditions such as sticking valves, lifters, etc., which could alter the flow into the combustion chamber. Refer to Symptoms - Engine Mechanical.

[asilverblazer]

Action Taken When the DTC Sets

• DTCs P0300–P0308 are Type B DTCs.
• When a catalyst damaging level of misfire is present, the ECM may disable the fuel injectors for up to 2 misfiring cylinders and will flash the malfunction indicator lamp (MIL).

Conditions for Clearing the DTC

DTCs P0300–P0308 are Type B DTCs.

Diagnostic Aids

• A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect for the conditions listed below:
  • A tire or wheel that is out of round or out of balance
  • Variable thickness brake rotors
  • An unbalanced drive shaft
  • Certain rough road conditions
  • Transmission operation
  • A damaged or defective accessory drive component or belt
• High resistance in the circuits of the injectors may set a misfire DTC without setting an injector DTC. Test the injector circuits of the affected cylinder(s) for a high resistance if you suspect a condition.
• If the condition is intermittent, observing the scan tool IC Circuit Test and Fuel Injector Circuit Test Status parameters may help isolate the condition. The circuit test status parameters will change from OK or Not Run to Fault/Malfunction if a condition exists.
• A condition in the heated O2 sensor (HO2S) heater control circuits may set a DTC P0300.

Reference Information

Description and Operation

• Electronic Ignition System Description
• Fuel System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

 

Control Module References for scan tool information

Special Tools

 

EL26792 - HEI Spark Tester

 

For equivalent regional tools, refer to Special Tools.

Circuit/System Verification

Note: Before starting the engine, review the freeze frame failure records data to determine if the misfire sets during a cold start or at operating temperature. If there is a cold start condition and the engine is started, the engine will need to be cooled down before the next attempt to start the engine within the fail conditions.

1. Engine Running at normal operating temperature.
2. Verify there is no abnormal engine noise.
   • If abnormal engine noise is present
     Refer to Symptoms - Engine Mechanical.
    
   • If abnormal engine noise is not present
   
   
3. Perform the scan tool Crankshaft Position Variation Learn procedure.
4. Verify no DTCs are set.
   • If any DTCs other than P0300–P0308 are set
     Refer to Diagnostic Trouble Code (DTC) List - Vehicle.
   • If DTC P0300–P0308 is set
     Refer to Circuit/System Testing.
    
   • If no DTCs are set
   
   
5. Verify the scan tool Cylinder 1–8 Current Misfire Counter parameters do not increment.
   • If increments
     Refer to Circuit/System Testing.
    
   • If does not increment
   
   
6. Engine Running, perform the Cylinder Power Balance Test with a scan tool.
7. Verify the engine speed changes when each injector is disabled and then enabled.
   • If engine speed does not change
     Refer to Circuit/System Testing.
    
   • If engine speed does change
   
   
8. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
9. Verify the DTC does not set.
   • If the DTC sets
     Refer to Circuit/System Testing.
    
   • If the DTC does not set
   
   
10. All OK.

Circuit/System Testing

Note: An erratic or weak spark is considered a no spark condition.

1. Verify none of the following conditions listed below exist:
   • Damage, carbon tracking, or fluid intrusion of the spark plug boots and/or spark plugs
   • Vacuum hose splits, kinks, and incorrect connections
   • Engine vacuum leaks
   • Crankcase ventilation system for vacuum leaks
   • Fuel pressure that is too low or too high. Refer to Fuel System Diagnosis.
   • Contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
   • Exhaust system restrictions
     • If a condition exists
       Repair or replace as necessary.
      
     • If no conditions exist
     
     
      
2. Ignition OFF, connect the EL 26792 - HEI Spark Tester to the appropriate spark plug wire, engine Cranking.
3. Verify the spark output.
   • If no output or the output is weak
     Refer to Electronic Ignition System Diagnosis.
    
   • If the output is good
   
   
4. Ignition OFF.
5. Verify the conditions listed below. Refer to Ignition System Specifications.
   • The correct spark plug type
   • The correct spark plug gap
   • The correct spark plug torque
    
   • If a condition exists
     Repair or replace as necessary.
    
   • If no conditions exist
   
   
6. Exchange the suspect spark plug with another cylinder that is operating correctly.
7. Engine Running.
8. Verify the scan tool Cylinder 1–8 Current Misfire Counter does not increment for the cylinder where the suspect spark plug was installed.
   • If increments
     Replace the spark plug.
    
   • If does not increment
   
   
9. Test or inspect for the conditions listed below:
   • A lean or rich Q17 Fuel Injector—Refer to Fuel Injector Balance Test.
   • An engine mechanical condition—Refer to Symptoms - Engine Mechanical.

Repair Instructions

Gas Engine Ignition Spark Plug Replacement

Repair Verification

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Turn OFF the ignition for 60 s.
5. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.
6. Engine Running, verify the scan tool Cylinder 1–8 Current Misfire Counter parameters do not increment.
   • If the misfire counter parameters increment, a misfire condition still exists.
   
   
7. To verify that the performance of the catalytic converter has not been affected by the condition that set this DTC, perform the Repair Verification for DTC P0420 or DTC P0430. Refer to DTC P0420 or P0430.

[asilverblazer]

I thought this snippet from the P0300 code was interesting:

"When a catalyst damaging level of misfire is present, the ECM may disable the fuel injectors for up to 2 misfiring cylinders and will flash the malfunction indicator lamp (MIL)."

[ktuck]

On 5/2/2024 at 1:25 PM, asilverblazer said:

Perhaps its the opposite then - all the others cylinders are getting too much fuel, then the O2 sensors are picking it up and leaning them all out. Essentially an injector balance issue. Because 2 and 5 are flowing the least amount of fuel, when their respective bank gets leaned out because all the other injectors on the bank are flowing too much it causes a miss fire in the leanest of the injectors. 

 

What would happen if injector for 2 was swapped with 3 so that the two miss firing injectors are on the same bank? I would expect the two banks to have significantly different fuel trims then. This would also confirm it is in fact a fueling issue. 

 

It could also be a different type of valve train issue not associated with a collapsed lifter. 

 

Has a compression check been performed?

Thank you for your suggestions and the very comprehensive diagnostic aids as well. That is what I have been looking for, circuit testing procedures and factory parameters of sensors and devices associated with the ECM.

 

I had run a compression check a few weeks ago, the results were not as I had hoped as all were on the low side, but at least they were similar throughout ranging from 120-135. I thought a very clean engine with just 114K would have higher compression numbers, but I don't believe they are low enough to cause a misfire. Also, my compression gauge is very old, (around 50 yrs!) and possibly not too accurate anymore. It has mostly been laying in a drawer in my toolbox forever. The injectors have been replaced twice so 2 and 5 have already had new injectors yet they continue to misfire. I have detected no evidence of fuel in the crankcase at any time in recent weeks.

 

Looking at some of the circuit testing, I noticed that I have one sensor (MAP) that is reporting out of range. It is 9.2psi at idle and spec is 2.7-6psi. I don't know how big a deal this is or not.  I have tested for vacuum leaks and found none (but wouldn't a vacuum leak cause positive trims anyway?). What I do know is that the misfires occur immediately upon cold start...the engine does not have to warm up for the misfiring to be felt and show up on the scanner. So, open or closed loop, doesn't matter.

 

Newdude recommended I get rid of the denso O2 sensor I replaced recently and go with a GM OEM sensor. I plan to do that when I return to Ky tomorrow. Also there are two modifications I have done to the truck in the two years I've owned it, both about a year and a half ago. One was a cat-back Borla dual exhaust system. The other was adding a S & B CAI system. I'm guessing the Borla exhaust isn't causing me this problem, but perhaps the CAI is. Also, a few weeks ago, I messed up and incorrectly cleaned my MAF sensor. I used CRC brakleen which I now know is a big time no-no. Thankfully, I saved my original air filter box and induction system, so I am going to remove the CAI and put it all back as it came originally along with a new MAF sensor. After this, if the problem remains unaffected, I'm not sure what to do. Possibly go ahead and pull the heads and look for problems internally? Any other ideas would be appreciated, thanks.

 

 

[asilverblazer]

The compression seems fine to me.

 

While I am also suspect of some sensors, the MAP out of spec, the MAF getting hosed with brake cleaner and the non factory O2 sensor. The open loop miss fires rules out a lot of things, and to me points back at injectors.

 

My next step would be the injector balance test. 

 

Quote

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

Two methods of testing fuel injector balance are available, the Active Fuel Injector Tester (AFIT) or a scan tool. The Active Fuel Injector Tester and SIDI adaptor connects to the engine control module harness connectors to test the high pressure fuel pump performance, fuel injector wiring, and fuel injector operation. The AFIT displays step by step instructions to precisely determine pressure drop of each fuel injector. The scan tool fuel injector balance test is performed while the engine is running at idle. The scan tool pressurizes the fuel rail to a predetermined pressure before each fuel injector is pulsed for a precise amount of time allowing a measured amount of the fuel to be injected. This causes a drop in the system fuel pressure that is recorded and used to compare each fuel injector.

Diagnostic Aids

• Monitoring the scan tool Cylinder 1 -8 Current Misfire Counters may help to isolate the fuel injector that is causing the condition.
• Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

 

Component Connector End Views

Description and Operation

 

Fuel System Description

Scan Tool Reference

 

Control Module References for scan tool information

Special Tools

• CH-47976 - Active Fuel Injector Tester
• CH-47976-500 - Active Fuel Injection Tester (AFIT) SIDI Adapter Kit

 

For equivalent regional tools, refer to Special Tools

Circuit/System Verification

1. Ignition ON.
2. Verify the scan tool Fuel Remaining parameter is greater than 10%.
   • If the Fuel Remaining parameter is less than 10%, add fuel to the fuel tank.
    
   • If the Fuel Remaining parameter is 10% or greater
   
   
3. Verify the scan tool ECT Sensor parameter is less than 60°C (140°F).
   • If the ECT Sensor parameter is greater than 60°C (140°F), allow the engine temperature to cool.
    
   • If the ECT Sensor parameter is 60°C (140°F) or less
   
   
4. Verify the battery is fully charged and all accessories are Off.
   • If the battery is not fully charged, charge or repair battery as necessary.
    
   • If the battery is fully charged
   
   
5. Preform the appropriate Fuel Injector Balance Test in Circuit System Testing.

Circuit System Testing

Fuel Injector Balance Test with Active Fuel Injector Tester

1. Ignition OFF, all vehicle systems OFF. Install the CH-47976 - Active Fuel Injector Tester and the CH-47976-500 - Active Fuel Injection Tester (AFIT) SIDI Adapter Kit , refer to the Active Fuel Injector Tester User Guide. It may take up to 2 minutes for all vehicle systems to power down.
2. Turn ON the Active Fuel Injector Tester and select the vehicle.
3. Ignition ON, perform the Injector Test with the Active Fuel Injector Tester.
   • If the Active Fuel Injector Tester aborts testing due to fuel pressure or fuel leak down
     Refer to Fuel System Diagnosis.
    
   • If the Active Fuel Injector Tester does not abort testing
   
   
4. Compare the test results with the appropriate recommended tolerance.
   • If any fuel injector exceeds the recommended tolerance
     Replace the appropriate Q17 Fuel Injector(s).
    
   • If all fuel injectors are within the recommended tolerance
   
   
5. Perform Fuel Injector Circuit Diagnosis.

Fuel Injector Balance Test with Scan Tool

 

Note: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

 

Note: The engine speed must be between 600–1,000 RPM to perform this test.

Note: For engines with 2 banks of cylinders, only measure average pressure drop on cylinders that are on the same bank.

1. Ignition ON.
2. Command the Fuel Pump Enable ON with a scan tool.
3. Verify the fuel pressure is between 320–580 kPa (46–84 PSI) with the fuel pump running.
   • If not within 320–580 kPa (46–84 PSI)
     Refer to Fuel System Diagnosis.
    
   • If within 320–580 kPa (46–84 PSI)
4. Verify the fuel pressure does not decrease greater than 34 kPa (5 PSI) within 1 minute.
   • If greater than the specified value
     Refer to Fuel System Diagnosis.
    
   • If less than the specified value
   
   
5. Engine idling.
6. Verify the scan tool Fuel Rail Pressure Sensor 1 parameter is between 1.9–5.0 MPa (276–725 PSI).
   • If not between 1.9–5.0 MPa (276–725 PSI)
     Refer to Fuel System Diagnosis.
    
   • If between 1.9–5.0 MPa (276–725 PSI)
7. Select the Fuel Injector Balance function within the Control Functions menu of a scan tool.
8. Select and test a Q17 Fuel Injector. Repeat for each Q17 Fuel Injector.
9. Obtain and record a pressure drop value for each Q17 Fuel Injector.
10. Add all of the individual pressure drop values except for the fuel injector suspected of being faulty. This is the total pressure drop.
11. Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop.
12. Multiply the average pressure drop by 0.20. This is the acceptable variance from the average pressure drop, 20%.
13. Verify the difference between any individual pressure drop and the average pressure drop is not greater than the acceptable variance.
    • If greater than the acceptable variance
      Replace the Q17 Fuel Injector.
     
    • If within the acceptable variance
    
    
14. Perform Fuel Injector Circuit Diagnosis.

 

[ktuck]

Just a general note to everyone in reference to purchasing O2 sensors from Rockauto. I have used RA many times and basically well pleased. However, this recent purchase of what was advertised on their site as GM Genuine Parts made by AC/Delco turned out not to be correct. When I opened the box to look at the sensors, staring at me on the upper housing of the sensor was the word DENSO! No wonder they were only 46 bucks. If you go to this part and click on their "info" icon, their description further indicates this is a Delco made part. I'm sorry, but this is false advertising, and in my case will cost me more time and trouble. I have already re-ordered the sensors from a different provider and had to pay for faster shipping because this is holding up the works for on this Silverado. The real kicker was that Rockauto will not pay for my return shipping of a couple sensors they misled me about. So, basically that means I paid for shipping the wrong sensors to me and now I get to pay to return those same wrong sensors! Okay, there's my rant for the day, but just be forewarned.

[ktuck]

3 hours ago, asilverblazer said:

The compression seems fine to me.

 

While I am also suspect of some sensors, the MAP out of spec, the MAF getting hosed with brake cleaner and the non factory O2 sensor. The open loop miss fires rules out a lot of things, and to me points back at injectors.

 

My next step would be the injector balance test. 

 

 

Thanks blazer, that makes sense to me. I will proceed with that when my new O2 sensors arrive. The truck is not runnable right now because I had to cut the wire harness pigtail on the bank one sensor so I could get a socket on it, could not break free with wrench. It was the only way I could remove the sensor, working on it from underneath on jackstands.

 

Another concern I have is about fuel pressure. My high pressure seems to be running within spec, but the low pressure pump(i'm guessing the one in the fuel tank??) shows quite a variable reading. It generally shows around 55 psi, but at times swings as far south as 25 and other times well over 60. I do not know if that is a normal reaction due to engine load or other variables, but I agree this is shaping up a lot like it is some kind of fuel related problem.

[asilverblazer]

1 hour ago, ktuck said:

the low pressure pump(i'm guessing the one in the fuel tank??) shows quite a variable reading. It generally shows around 55 psi, but at times swings as far south as 25 and other times well over 60. I do not know if that is a normal reaction due to engine load or other variables, but I agree this is shaping up a lot like it is some kind of fuel related problem.

Pressure on the low pressure side is questionable... like the other 'questionable' items though with no way of corelating it to the miss firing cylinders I would not focus heavily on it.

 

If you had a data log that had all PID's when the miss fire was occurring so that you could see if the MAP, MAF, O2 sensors or fuel pressure was out of spec during the miss fire then I would rule them out because a malfunction of those items would not be cylinder 2 and 5 specific.

[ktuck]

On 5/6/2024 at 2:03 PM, ktuck said:

Just a general note to everyone in reference to purchasing O2 sensors from Rockauto. I have used RA many times and basically well pleased. However, this recent purchase of what was advertised on their site as GM Genuine Parts made by AC/Delco turned out not to be correct. When I opened the box to look at the sensors, staring at me on the upper housing of the sensor was the word DENSO! No wonder they were only 46 bucks. If you go to this part and click on their "info" icon, their description further indicates this is a Delco made part. I'm sorry, but this is false advertising, and in my case will cost me more time and trouble. I have already re-ordered the sensors from a different provider and had to pay for faster shipping because this is holding up the works for on this Silverado. The real kicker was that Rockauto will not pay for my return shipping of a couple sensors they misled me about. So, basically that means I paid for shipping the wrong sensors to me and now I get to pay to return those same wrong sensors! Okay, there's my rant for the day, but just be forewarned.

I need to correct my post from yesterday about the O2 sensors from Rockauto. I was wrong. The sensors I received were in fact GM sensors. I went to a local Chevy dealer to purchase the OEM sensors directly from them and learned that they too have Denso printed on the body of the sensor.  The parts manager there got me straightened out on this. Denso is making O2 sensors for GM currently. The bank one sensor I removed yesterday has Denso printed on it and it is the O2 sensor that came with the vehicle when new. Denso does make a sensor of its own that they market for a much lower price and is not very user-friendly with GM ECMs. The OEM sensor will have the 8-digit GM part number at the top of the sensor housing and the word Denso directly below. The regular Denso sensor will not have the GM part number on it. So, bottom line, Rockauto sent me the correct sensors after all.

[ktuck]

On 5/6/2024 at 4:06 PM, asilverblazer said:

Pressure on the low pressure side is questionable... like the other 'questionable' items though with no way of corelating it to the miss firing cylinders I would not focus heavily on it.

 

If you had a data log that had all PID's when the miss fire was occurring so that you could see if the MAP, MAF, O2 sensors or fuel pressure was out of spec during the miss fire then I would rule them out because a malfunction of those items would not be cylinder 2 and 5 specific.

Okay, I'm gonna try to make this as brief as possible by just listing some observations and data values from the scan tool. I replaced both upstream O2 sensors with OEM sensors. The bank two upstream sensor(denso) I changed out around a month ago was coated in jet black soot. Bank one upstream sensor(the original one) looked normal by comparison. Original air box, air filter and air induction system reinstalled, CAI removed. A new MAF sensor installed.

 

MAP sensor was reading within normal range (between 3.48 and 4.28) entire time of testing(over an hour). Five of the injectors failed the fuel injector balance test. All 4 cylinders on bank 2 failed and by a considerable amount. the only one to fail on bank 1 was #5 which for some reason is now the main misfiring cylinder by far (over 11,000 misfires, the next highest was just around 450). Surprising was that cylinder 2 is basically not misfiring at all and it was the worse one up until now. That shows the issue has moved from at least one cylinder and stopped misfiring altogether. Would this mean I do not have an internal issue with the valvetrain? To me, there is no reason for it to change after steadily misfiring for weeks now. Another change, the misfires on #5 increased exponentially upon increasing throttle position. At idle only #5 and occasionally #7 misfired. Upon acceleration, several other cylinders misfired as well, but none anywhere near the extent of #5. The LTFT trim numbers were around -30 for bank 2 and -16 for bank 1. I drove the truck for a short distance of about 4 miles. The traction control light came on as soon as I got out on the highway along with a flashing CEL. The CEL went off a time or two but mainly was flashing. I might have run the truck too long while reading the scan tool and it went into open loop and stayed there. It the set P0171 and P0174 lean codes and fuel trim numbers where halted...they all showed no reading, just blank. The average STFT for both banks was 25 and the average LTFT for both banks was 35. I guess that is an automatic reading when it goes in open loop. I am going to repeat the injector balance test tomorrow just make sure I get consistent results. I also am going to hook up my other scan tool and do comparisons of various readings. So, as I see it, the only thing definitive about my readings is that apparently, I still have an injector problem. Can I have my injectors tested? If so, how to I go about that? After all, this is the second set of GM injectors I've installed.

[asilverblazer]

15 hours ago, ktuck said:

The bank two upstream sensor(denso) I changed out around a month ago was coated in jet black soot. Bank one upstream sensor(the original one) looked normal by comparison.

Bank 2, with the black O2 sensor also failed all all the injectors on the balance test - over fueling bank 2. 

 

15 hours ago, ktuck said:

Surprising was that cylinder 2 is basically not misfiring at all and it was the worse one up until now. That shows the issue has moved from at least one cylinder and stopped misfiring altogether. 

I don't think the issue 'moved'.

 

15 hours ago, ktuck said:

Would this mean I do not have an internal issue with the valvetrain? 

I don't suspect a valvetrain issue. 

 

15 hours ago, ktuck said:

I replaced both upstream O2 sensors with OEM sensors. Original air box, air filter and air induction system reinstalled, CAI removed. A new MAF sensor installed...

 

To me, there is no reason for it to change after steadily misfiring for weeks now. 

The changes you made could have cleaned up some of the miss firing problem on cylinder 2.

 

15 hours ago, ktuck said:

The only one to fail on bank 1 was #5 which for some reason is now the main misfiring cylinder by far (over 11,000 misfires, the next highest was just around 450)... Another change,

the misfires on #5 increased exponentially upon increasing throttle position. At idle only #5 and occasionally #7 misfired. Upon acceleration, several other cylinders misfired as well, but none anywhere near the extent of #5... The traction control light came on as soon as I got out on the highway along with a flashing CEL. The CEL went off a time or two but mainly was flashing...

Cylinder 5 is definitely a problem. "Some" amount of miss fires are acceptable and normal. It seems that the other 7 cylinders might be with in that tolerance.

 

15 hours ago, ktuck said:

The LTFT trim numbers were around -30 for bank 2 and -16 for bank 1. I drove the truck for a short distance of about 4 miles. The traction control light came on as soon as I got out on the highway along with a flashing CEL. The CEL went off a time or two but mainly was flashing. It then set P0171 and P0174 lean codes and fuel trim numbers where halted...they all showed no reading, just blank. The average STFT for both banks was 25 and the average LTFT for both banks was 35. 

If you made all the changes to the air intake above then recorded this test I would unplug the battery for a while to reset then retest again. The intake changes may have 'surprised' the PCM.

Quote

Diagnostic Aids

• Allow the engine to reach operating temperature. With the engine running, observe the HO2S parameter with a scan tool. The HO2S value should vary from approximately 40 mV to approximately 900 mV, and respond to fueling changes.
• The normal Short Term Fuel Trim and Long Term Fuel Trim parameters should be between +10 and −10 % with 0 % the optimum, with the engine running at operating temperature.
• Any un-metered air into the engine causes this DTC to set. Thoroughly inspect all areas of the engine for vacuum leaks.
• A MAF sensor condition can cause this DTC without setting a MAF DTC. If there is a MAF sensor condition, the MAF sensor parameters will appear to be within range.
• Inspect the air filter for being the correct one for this application. Make sure that the engine oil fill cap is in place and that it is tight. Verify that the engine oil dip stick is fully seated.
• Certain aftermarket air filters may cause a DTC to set.
• Certain aftermarket air induction systems or modifications to the air induction system may cause a DTC to set.
• Certain aftermarket exhaust system components may cause a DTC to set.

 

Since you know the LTFT trims...

Quote

1. • If less than −10 %
    
   1. Ignition OFF.
   2. Inspect for the conditions listed below:
      • Mass air flow (MAF) sensor signal skewed—If the Short Term Fuel Trim parameters for both banks changes greater than 20 % when the MAF sensor is disconnected, refer to DTC P0101.
      • Contamination of the mass air flow sensor with oil or other foreign material.
      • Fuel contamination—Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
      • Missing, restricted, or leaking exhaust components—Refer to Symptoms - Engine Exhaust.
      • Malfunctioning fuel injectors—Refer to Fuel Injector Diagnosis.
      • Collapsed or restricted air intake duct.
      • Excessive fuel pressure — Refer to Fuel System Diagnosis.
      • Dirty or restricted air filter.
      • Objects blocking the throttle body.
      • Improper operation of the evaporative emissions control system.
      • Excessive fuel in the crankcase—Change the engine oil as necessary.
        • If a condition is found, repair as necessary.
        • If no condition is found, inspect the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical.

 

15 hours ago, ktuck said:

I am going to repeat the injector balance test tomorrow just make sure I get consistent results. So, as I see it, the only thing definitive about my readings is that apparently, I still have an injector problem. Can I have my injectors tested? If so, how to I go about that? After all, this is the second set of GM injectors I've installed.

I would definitely repeat the injector balance test. What injector test are you using? Fuel Injector Balance Test with Active Fuel Injector Tester or Fuel Injector Balance Test with Scan Tool

 

This many failed injectors is also suspect, are they from a dealer or could they be from 'somewhere' else that might be counterfeit?

 

If the bank of cylinders fails again, I would look at fuel rails and lines. Also, note that in the above excessive fuel pressure could cause some issues. Is the fuel rail pressure remaining in tolerance?

Edited May 8, 2024 by asilverblazer

[ktuck]

4 hours ago, asilverblazer said:

Bank 2, with the black O2 sensor also failed all all the injectors on the balance test - over fueling bank 2. 

 

I don't think the issue 'moved'.

 

I don't suspect a valvetrain issue. 

 

The changes you made could have cleaned up some of the miss firing problem on cylinder 2.

 

Cylinder 5 is definitely a problem. "Some" amount of miss fires are acceptable and normal. It seems that the other 7 cylinders might be with in that tolerance.

 

If you made all the changes to the air intake above then recorded this test I would unplug the battery for a while to reset then retest again. The intake changes may have 'surprised' the PCM.

 

Since you know the LTFT trims...

 

I would definitely repeat the injector balance test. What injector test are you using? Fuel Injector Balance Test with Active Fuel Injector Tester or Fuel Injector Balance Test with Scan Tool

 

This many failed injectors is also suspect, are they from a dealer or could they be from 'somewhere' else that might be counterfeit?

 

If the bank of cylinders fails again, I would look at fuel rails and lines. Also, note that in the above excessive fuel pressure could cause some issues. Is the fuel rail pressure remaining in tolerance?

 

I did the injector balance test with an Autel scan tool. The injectors I installed were GM part # 12668390 which was the same GM number on the original injectors I took out of it. I purchased them from an individual on ebay who according to his feedback, had positive comments on his transactions. However, newdude indicated that part number is quite old and possibly I received some that were less than perfect. Right now, that is looking like a real possibility in my view given what all else has been done on this truck. The fuel pressure readings are staying in spec from what I've observed.

 

I triggered a new code while I had the scan tool hooked to it last night, a P0097, intake air temperature sensor 2 circuit low. Oddly, the scan tool readings showed IAT sensor 1 around 113 when fully warmed up, but sensor 2 about 144.  It set as a permanent code along with my other 3 permanent codes, P0300, P219A, and P050D. The P0171 and P0174 codes only showed up as pending during my testing which might have been what triggered them. The condition I have now is the fuel system is staying in open loop even though the truck has been fully warmed up and coolant temp around 190 or better. This has locked out my fuel trim numbers, and I don't believe the O2 sensors are functioning normally either. I was able to conduct another fuel injector balance test, but the results were affected by the open loop status and isn't a valid test I'm sure, especially since this time none of the injectors failed. I disconnected the battery for a couple hours today on hopes that would take care of the staying in open loop...it didn't. While running a test with the scanner, it briefly went into closed loop but less than a minute later went back to open loop and has stayed that way ever since. What is it going to take to get it out of open loop?

 

At this point, I can't help but wonder if I could have a faulty ECM/PCM? Back in the day when I worked on computer command control feedback carburetor systems in the 80s, I recall among the possible codes that could be set were a few codes that actually pertained to the ECM itself. Of course, there were times when a computer got smoked in such a way it hadn't the capability to diagnose itself. I recall changing quite a few when I worked for a Chevy dealer. All one had to do was remove the chip from the old one and install in the new one and often that corrected the problem. However, from what I have read about the systems we have now, it appears ECM failures are not as common.