DTC Codes P0152 & P0102

[Durkin]

Folks:

 

Does any one here know what causes DTC Codes P0152 & P0102 to be thrown occaisionally? As to P0152, what causes the heater voltage to be too high? Would the blower cause the MAF to go out of range, especially now that I have a 3" pulley? The codes get set simultaneously at a normal highway speed and acceleration, not at WOT necessarily.

 

Regards,

 

Durkin

[Haulin' 8.1]

The MAF code is set by it reading a lower airflow rate than what's possible based on conditions and the O2 code is set by the O2 heater reading high voltage (from running rich) for longer than 165 seconds.

 

If you understand engine controls like I do you realize that these two codes setting at the same time would be unlikely without a electrical failure. Actually the PCM is supposed to block a 152 if a 102 is already present as MAF malfuntions will cause fuel mixture problems. But the thing is a low MAF reading like yours should cause a lean mixture before the code sets so the two happening at the same time don't make sence.

 

I think you have a shorted wire harness, probably these two circuits contact each other. If the two made contact the MAF signal would drop and the 02 heater voltage monitor would read high. And if one prevents the other from setting this would explain how they both set at the same time.

 

Check your harness carefully, especially near aftermarket equipment. I've seen similar problems caused by a K&N filter laying on a wire harness. The filter screen rubbed through and shorted several wires causing all kinds of codes and driving me up the wall trying to determine why. A Chilton manual will have the PCM wire harness diagram in it but the Helms manual would be invalueable.

 

Vernon

[GM-Tech]

If you understand engine controls like I do you realize that these two codes setting at the same time would be unlikely without a electrical failure.

 

It's important to remember that both of those DTC's only turn on the MIL on the SECOND CONSECUTIVE ignition cycle that they fail the test.

 

So if one is just judging by, "hey, the light came, lets check the codes" and you find both, it doesn't mean they both set at the exact same moment. It isn't mentioned so I don't know if that's the diagnostic process being used.

 

Lets say P0152 fails for the first time and sets the code. There's no light turned on. 20 miles later, P0102 sets. Still no light because it's the first failure for that one too. Now on the next ignition cycle, P0152 fails again. Now the light is turned on. You check the DTCs and find both P0102 and P0152, and figure they both set at the same time and turned the light on, but that is not the case in this example.

 

You need to look at freeze frame data and failure records. That will tell you a little more about what and when this all happened.

[Haulin' 8.1]

GM Tech, I see your point but I don't understand the part about about "Conditions for Running the DTC" for a P0152. When it says that DTCs...P0102... are not set. I take that to mean that if the PCM already records a MAF problem it disregards codes that would be set from the effects of it. Is there something I'm missing? I got the information from the Helms books.

Thanks,

Vernon