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Cel Flashing At Me


fataugie

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I have a quick question....I have a 2003 2500HD 4x4 GMC with a 6.0L automatic. I filled up today and added a large size Chevron Techtron gas treatment bottle right before a long trip. About 50 miles into the trip, I started getting the engine light flash at me for a few seconds, then it would go away, then it would flash again 10 miles further, etc. It eventually mellowed out some and I see that flashing means it's misfiring so I would take it out of cruise and slow down, speed up, etc until it went away. All the time, the truck was running smooth, the gauges were all in the proper ranges and I couldn't tell there was something wrong except for the light.

 

Could it be pinging (maybe crappy gas)? Could it be the treatment? I see from searches it could be 10 other things so it could just be a coincidence, but I doubt it.

 

I haven't treated the gas in probably a year and 15K, but this is the first time I ever had a problem like this. I haven't been to Autozone yet, so I don't have any codes to offer yet. Any ideas before I make an appointment to get it checked?

 

UPDATE: I just had the codes read....0300 random/multiple cylinder misfire. While I was out, I went ahead and topped off the tank with fuel from a different (trusted) source. It never flashed during my 30+ mile round trip, but the only time it flashed the last time was at expressway speeds of 70+ and I didn't reach those on this trip so who knows.

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  • 2 years later...
I have a quick question....I have a 2003 2500HD 4x4 GMC with a 6.0L automatic. I filled up today and added a large size Chevron Techtron gas treatment bottle right before a long trip. About 50 miles into the trip, I started getting the engine light flash at me for a few seconds, then it would go away, then it would flash again 10 miles further, etc. It eventually mellowed out some and I see that flashing means it's misfiring so I would take it out of cruise and slow down, speed up, etc until it went away. All the time, the truck was running smooth, the gauges were all in the proper ranges and I couldn't tell there was something wrong except for the light.

 

Could it be pinging (maybe crappy gas)? Could it be the treatment? I see from searches it could be 10 other things so it could just be a coincidence, but I doubt it.

 

I haven't treated the gas in probably a year and 15K, but this is the first time I ever had a problem like this. I haven't been to Autozone yet, so I don't have any codes to offer yet. Any ideas before I make an appointment to get it checked?

 

UPDATE: I just had the codes read....0300 random/multiple cylinder misfire. While I was out, I went ahead and topped off the tank with fuel from a different (trusted) source. It never flashed during my 30+ mile round trip, but the only time it flashed the last time was at expressway speeds of 70+ and I didn't reach those on this trip so who knows.

Did you ever figure this out, my 2003 Silverado 2500HD ECLB 6.0L, 136,000 miles. It is doing the exact same thing, the light only blinks at speeds over 70mph. I slow down and it goes off, it is driving me nuts.

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Get in line. You're the 5th or 6th person this month alone to make a thread about it. As far as I know, nobody has found a solution, and no dealer wants to take a guess. From what I gather, the things that people, including myself, have tried are : air filter (switching from K&N to dry filter), MAF sensor, plugs and wires (various brands), crankshaft relearn, different octane gas for a few tanks, O2 sensor(s), and more. Like I said, I haven't read of anyone solving this issue. Do some searching through the HD section and you'll find some threads about it.

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Get in line. You're the 5th or 6th person this month alone to make a thread about it. As far as I know, nobody has found a solution, and no dealer wants to take a guess. From what I gather, the things that people, including myself, have tried are : air filter (switching from K&N to dry filter), MAF sensor, plugs and wires (various brands), crankshaft relearn, different octane gas for a few tanks, O2 sensor(s), and more. Like I said, I haven't read of anyone solving this issue. Do some searching through the HD section and you'll find some threads about it.

I have seen all the threads on this but on my truck I don't think it actually has a miss at least I can't feel one. My light just blinks when I go over 70mph. My dealer says it needs an injector clean but it still has plenty of power.

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This may help

 

97-05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires on One Bank - kw CEL diagnostics driveability DTC P0171 P0172 P0174 P0175 P0300 P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308 #PIP3056 - (Jul 12, 2004)

97 - 05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires On One Bank

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The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.

 

Condition/Concern:

Check Engine Light with a P0300 due to 2 - 4 cylinders misfiring on the same bank of the engine. DTCs P0171, P0172, P0174 or P0175 may also set for the misfiring bank.

 

Recommendation/Instructions:

If the published misfire diagnostic does not isolate the cause, perform the following suggestions as necessary:

 

Perform a fuel injector balance test for all 8 cylinders. If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector.

Inspect O2 sensor connections on the misfiring bank for corrosion or water intrusion. If water intrusion is found on the right bank, it may be due to the AC Evaporator Condensation dripping onto the O2 sensor harness. If this condition is found, reposition and shield the harness to prevent a repeat concern and repair the connections.

Check for excessive exhaust backpressure using the restricted exhaust diagnosis from SI.

Swap the Position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor.

.

 

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

 

Models:

(00 - 05 Cadillac Escalade - C6 and K6) and (02 - 05 Chevrolet Avalanche - C1, C2 K1 and K2) and (99 - 05 Chevrolet Silverado - C1, C2 K1 and K2) and (00 - 05 Chevrolet Suburban - C1, C2, K1 and K2) and (00 - 05 Chevrolet Tahoe - C1 and K1) and (99 - 05 GMC Sierra C1, C2 K1 and K2) and (00 - 05 GMC Yukon - C1, C2, K1 and K2) and (03 - 05 Chevrolet Express G1, G2, G3, H1, H2 ) and (03 - 05 GMC Savana G1, G2, G3, H1, H2 ) and (04 - 05 Buick Rainier S1, T1 ) and (03 - 05 Chevrolet Trail Blazer EXT S1, T1 ) and (03 - 05 GMC Envoy XL XUV S1, T1 ) and (03 - 05 Hummer H2) and (04 - 05 Cadillac CTS-V DB) and (98 - 02 Chevrolet Camaro FB) and (97 - 04 Chevrolet Corvette YB) and (98 - 02 Pontiac Firebird FB) and (04 - 05 Pontiac GTO VB)

 

 

99-05 Full Size Trucks, Utilities and Vans with 4.8 5.3 6.0 V8 Engines That Have a P0300 Due to Fuel Contamination Cylinder 7 Misfire - kw CEL code contaminated DTC fuel gas L59 LM7 LR4 LQ4 LQ9 miss #PIP3055 - (Jul 8, 2004)

99 - 05 Full Size Trucks, Utilities and Vans with 4.8 5.3 6.0 V8 Engines That Have a P0300 due to Fuel System Contamination Cylinder 7 Misfire

.

 

The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.

 

Condition/Concern:

Service Engine Soon Light with a P0300 misfire due to misfires mainly on cylinder 7. A possible cause could be fuel contamination. If present, the contaminated fuel will collect around the #7 fuel injector due to the fuel rail configuration in these vehicles. This issue can also cause some random misfires on cylinder 2 and 8 since they are next to cylinder 7 in the firing order.

 

Recommendation/Instructions:

If the published misfire diagnostics does not isolate the concern, the following suggestions may help if the misfire is related to fuel contamination:

 

When the lines are removed, cap the fuel rail off to retain any fuel that might be contaminated. Remove the rail, drain it into a clear container and inspect for contamination.

If contamination is found, follow the Fuel System Cleaning procedure in Service Information.

Once the fuel system is cleaned, refill the fuel system with new gasoline.

Advise the customer that they should only use gasoline from a high quality, high volume filling station.

If this is a 99 - 00 Chevrolet Silverado or GMC Sierra, also review 00-06-04-024. This bulletin relates to an updated EVAP vent valve to prevent water from being drawn in through the EVAP Vent Valve, which may lead to repeat fuel contamination.

 

.

 

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

 

Models:

(01 - 05 Cadillac Escalade C1, C6, K1, K6) and (02 - 05 Chevrolet Avalanche C1, K1, C2, K2) and ((03 - 05 Chevrolet Express G1, G2, G3, H1, H2) and (99 - 05 Chevrolet Silverado Truck C1, K1, C2, K2, C3, K3 ) and (00 - 05 Chevrolet Tahoe C1, K1 ) and (00 - 05 Chevrolet Suburban C1, K1, C2, K2, C3, K3 ) and (03 - 05 GMC Savana G1, G2, G3, H1, H2 ) and (99 - 05 GMC Sierra Truck C1, K1, C2, K2, C3, K3 ) and (00 - 05 GMC Yukon C1, K1 ) and (00 - 05 GMC Yukon XL C1, K2, C2, K2, C3, K3) and (03 - 05 Hummer H2 N2 )

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More ..... Good Luck !

 

DTC P0300

System Description

The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way catalytic converter (TWC) to overheat under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the PCM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.

 

DTC Descriptor

This diagnostic procedure supports the following DTC:

 

DTC P0300 Engine Misfire Detected

 

Conditions for Running the DTC

DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0125, P0128, P0220, P0315, P0335, P0336, P0341, P0342, P0343, P0502, P0503, P1114, P1115, P1120, P1258 are not set.

The engine speed is between 450-5,000 RPM.

The ignition voltage is between 10-18 volts.

The engine coolant temperature (ECT) is between -7 and +130°C (+19 and +266°F).

The fuel level is more than 10 percent.

The throttle angle is steady within 1 percent.

The antilock brake system (ABS) and the traction control system (TCS) are not active.

The transmission is not changing gears.

The A/C clutch is not changing states.

The PCM is not in fuel shut-off or decel fuel cut-off mode.

The PCM is not receiving a rough road signal.

DTC P0300 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The PCM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards.

 

Action Taken When the DTC Sets

The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration:

Thickness variation of the brake rotors--Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes.

The drive shaft not balanced--Refer to Vibration Analysis - Driveline in Vibration Diagnosis and Correction.

Worn or damaged accessory drive belt--Refer to Symptoms - Engine Mechanical in Engine Mechanical - 4.8L, 5.3L and 6.0L.

There may be more or less cylinders actually misfiring than indicated by the scan tool.

Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.

If there are multiple misfires on only one bank, inspect the fuel injector and ignition coil, power and ground circuits for that bank. Refer to Engine Controls Schematics .

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Me too 85k. I have a new set of coils and injectors I will be installing this weekend...Who knows if it will change anything.

Changed all coils/brackets(rusted and coming apart) and all injectors and fuel rails runs real smoooth, more power...RFI problem is gone...engine light still flashes @ 70 Not 65,75,80,85....etc...Smooth-tons of power-no way it has a miss...? I have some new mapping software coming next week, I'll see if I can catch anything.Next may be the 70 mph "tree test" :thumbs:

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  • 8 months later...

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