p0172

**awsom83** · 01-12-2009

I have a 2001 Pontiac Grand Prix 3.8 non-supercharged engine. I recently replaced the t-stat and now I have DTC p0172 (rich code, bank 1). During first start up when engine is cold it will stumble and act like it wants to die, give it gas and it runs fine until you are at a stop light. I can turn the engine off and restart the engine and it will run fine after that. I have replaced the MAF, IAC Sol, Fuel Press Reg, and front o2 sensor. I also have a code p0336 (cranksensor) that I am going to replace as well, would the cranksensor set a rich code as well? Any suggestions would be GREAT!!!

Thank you

TDCRacing · 01-12-2009

The crank sensor is unlikley to set a rich code. Did you put in a colder thermostat in? I foget what the code is if you do this but that may be you're issue.

**awsom83** · 01-13-2009

I replaced it with a 195 t-stat, I am thinking maybe a ECT sensor? Or outside air temp sensor?

Thanks!!

**SyntheticShield** · 01-13-2009

Does the temp gauge on your dash seem to be working properly? Whats it reading when the engine is warmed up?

**awsom83** · 01-13-2009

Yes the temp gauge does work, when the vehicle is warmed up it reads around 200

**SyntheticShield** · 01-13-2009

Well I was hoping it wasnt reading anything at all or way off as that would have pointed to a possible bad coolant temperature sensor.

A crankshaft position sensor usually doesnt cause the symptoms you describe, but its also rare to get a code for a CPS as well. Ive had to replace two bad ones on mine and not once has it thrown a code for it and thats not uncommon.

So if you are getting a code for it, I would replace it, but Im not extremely confident that is what is causing your issue and as TDC stated, it wont cause you to run rich either unless the signal the CPS sends to the ignition control module is all out of whack like missing signals or something. But even if that were the case I would expect some sort of misfire code too.

**awsom83** · 01-13-2009

I am going to replace CPS this weekend due to the p0336 (CPS out of range) But yes I was thinking the samething about the CPS going bad and sending whacked out readings to the IGN module, but with not being any missfire codes I scrapped that idea. Just has me puzzled.

Thank you for you info!!

**cn1151** · 01-19-2009

I would think it would if the crank sensor was causing it to misfire. But I would think you would see some 300 codes. If this happened after you replaced the tstat I would be looking in that area for a loose connector or pinched wire. If you do decide to do the crank sensor you should think about the cam sensor while you’re in there. Good luck let us know how it turns out.

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