Help with O2 sensor readings.

[chas0218]

Here are 2 snap shots of what my PCM is seeing at 800 rpm and 2400 rpm. The sensor readings are pretty obscured and I am having a hard time making any sense of them. Is there anything else that looks out of the ordinary? It looks like the PCM won't allow the engine into Closed loop mode because of the readings. The DTC is a multiple cylinder random misfire and I can imagine why by these readings.

 

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Number of DTCs stored in this ECU 1

Fuel system 1 statusOL

Fuel System 2 statusOL

Calculated LOAD Value(%)4.3

Engine Coolant Temperature(¡£C)49

Short Term Fuel Trim -Bank 1(%)3.1

Long Term Fuel Trim - Bank 1(%)0.0

Short Term Fuel Trim -Bank 2(%)12.5

Long Term Fuel Trim - Bank 2(%)0.0

Intake Manifold Absolute Pressure(kPa)39.0

Engine RPM(rpm) 782

Vehicle Speed Sensor(km/h)0

Ignition Timing Advanece for #1 Cylinder(¡£)4.0

Intake Air Temperature(¡£C)-2

Air Flow Rate from Mass Air Flow(g/s)11.07

Absolute Throttle Position(%)12.5

Location of Oxygen SensorsB1S12--B2S12--

Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.825

Short Term Fuel Trim Bank 1-Sensor 1(%)1.6

Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.855

Short Term Fuel Trim Bank 1-Sensor 2(%)N/A

Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)0.065

Short Term Fuel Trim Bank 2-Sensor 1(%)14.1

Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.125

Short Term Fuel Trim Bank 2-Sensor 2(%)99.2

OBD requirements to which vehicle is designedOBDII

Power Take Off(PTO) StatusOFF

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Number of DTCs stored in this ECU 1

Fuel system 1 statusOL

Fuel System 2 statusOL

Calculated LOAD Value(%)12.2

Engine Coolant Temperature(¡£C)55

Short Term Fuel Trim -Bank 1(%)0.0

Long Term Fuel Trim - Bank 1(%)0.0

Short Term Fuel Trim -Bank 2(%)7.8

Long Term Fuel Trim - Bank 2(%)0.0

Intake Manifold Absolute Pressure(kPa)29.0

Engine RPM(rpm) 2338

Vehicle Speed Sensor(km/h)0

Ignition Timing Advanece for #1 Cylinder(¡£)31.5

Intake Air Temperature(¡£C)-2

Air Flow Rate from Mass Air Flow(g/s)11.24

Absolute Throttle Position(%)11.8

Location of Oxygen SensorsB1S12--B2S12--

Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.040

Short Term Fuel Trim Bank 1-Sensor 1(%)0.0

Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.100

Short Term Fuel Trim Bank 1-Sensor 2(%)N/A

Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)0.010

Short Term Fuel Trim Bank 2-Sensor 1(%)0.0

Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.060

Short Term Fuel Trim Bank 2-Sensor 2(%)99.2

OBD requirements to which vehicle is designedOBDII

Power Take Off(PTO) StatusOFF

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[BigDaddycat]

I had similar issues last year. Turns out all 4 of the sensors needed to be replaced. The two before the catalytic converter are identical, and the two after it are different but identical to each other. They all 4 look the same but two have female plugs and two have male plugs. They were really easy to replace if you have a couple of ramps you can drive up on. If you do this be sure to let the truck warm up about 2-3 minutes from being cold. This will help loosen the threads a little. Another issue you may be having is the throttle body may need cleaning. I did this also at the same time. You can find some good videos on Youtube showing exactly how to do it. Takes about 10 minutes from start to finish.

[chas0218]

I just replaced the upstream sensors. Would the down stream/post cat sensors play a role in the mixture?

[Duelin]

One of the things that I see from you snap shot is the engine is not up to temperature. Oxygen sensors must reach an operating temperature of about 600 degrees before they will begin to create any voltage. Once they start creating voltage the ecm looks at the voltage and the engine should go into closed loop. As far as looking at the snap shot of the o2 sensors it doesn't tell us anything. It is just a quick look at about a 20th of a second of information. You have to sit and watch the o2 sensors and see if they are switching back and forth between lean and rich. The best way to look at an o2 sensor is with a digital storage oscilloscope and look at a wave form. Also what brand of o2 sensor did you install. Some brands are't even worth buying. I have seen guys install cheap ones and they worked worse than the old ones they took out. I alway like to use OEM.

[travisstorma]

I just replaced the upstream sensors. Would the down stream/post cat sensors play a role in the mixture?

Down stream just monitors the cats. They don't influence the mixture.

[chas0218]

I was also wondering if a Cam sensor would make the engine run like this. I read somewhere that the PCM will open injectors all at once hoping to get an open intake valve.

 

I find this funny because I just got another code for Crank Position sensor circuit malfunction which has been replaced and the wiring is all in tact. Would a Cam sensor on the way out possibly cause errors on other sensors?

 

One thing that had me thinking to was that the misfires I have been getting are all after one another on the firing order.