Multiple Codes Help
 

I just took my car in for the state inspection and my machanic came back with the following codes:

U31D5
C3000 (this came up 3 times)
PODD6
P17CE
P12CF
PO100 (twice)

I can't find info for any but the last.

Any Help would be greatly appriciated!

Welcome to the forum.:) Was the CEL on before you took it in for inspection? Those codes look like an artifact of a bad OBD interface. Consider a visit to the service department. A Tech 2 scan tool should show the correct codes.

If you have a local AutoZone, they should be able to scan your vehicle and decipher any codes that show up.

Thank you,
While doing my own homework I found that most of these codes don't exist when I did a web search (First ever) with the exception of one site. A person with a Cadillac just 6 days ago in NH (where I am) had the same codes in the same order. He is having no luck finding out what they are also. I & my mechanic believe that they are all related to the Mass Air Flow sensor as that was the only code that I found with an explination.
I am going to change the Mass Air Flow Sensor this weekend and see if it clears all of the other codes.

What year Equinox is yours and what engine? P0100 may not even be defined for yours in which case it's another artifact of a garbled read.

I have a generic OBD scanner and the only code that was legit was P0100, which was the Mass or Volume Air Flow Circuit malfunction.
Hope that helped.

Sorry the Vehicle is a 2005 Equinox LT 3.4 V6.

This tomorrow I will be checking the wiring and voltage. New question, I see there is a Mass Air Flow Sensor Cleaner out there, would that cure the problem if the wiring and voltage is fine? The vehicle has 80k on it so the fact may be that it is time to change it anyways.

Originally the code was (forgot the number) for the cooling tempurature was not warm enough. I changed the thermostat (original 180 deg) to a 195 deg one and that seemed to clear that code but then sent these out. I did drive the vehicle approx 200 miles since clearing that code. The temp gauge read fine, not too hot or too cold and the car heat worked fine before I changed the thermo (and after).

Use either MAF cleaner or electronic parts cleaner. On yours the MAF sensor assembly includes the IAT sensor and thus is not trivial in terms of cost.

I guess I'm not convinced that you're actually seeing P0100 by itself when the ECM is perfectly capable of differentiating the trouble with P0101, P0102, or P0103. Can your OBD scanner display freeze frame data for this P0100? If so, do the parameters make sense?

While I was picking up the MAF cleaner I had Autozone check the engine light again. They again showed only P0128 (x2) a low temp coolant code. They showed no other codes. I am puzzled because when tested for the state inspection only the above codes not this one. I just took the hose off and checked the sensor. Inside it there is a ring of oil(? dirt) on the wall of the sensor around the flap. I cleaned that, the wires (non frayed or disconnected) and the connections. I also changed the air filter that was pretty bad. I hope this works if not I will check the voltage and continuity with my meter. If all else fails I will replace the sensor but at $115 I want to check everything else first.

Based on the description, it sounds like the "sensor" you checked was actually the throttlebody, and not a sensor at all. It sounds like you were seeing some carbon build-up around the throttle plate. This is normal, but it doesn't hurt to clean it up periodically.

Pay close attention to the temp gauge. The P0128 code is often an indicator of a thermostat that is stuck open. If the temp gauge never gets above the 1/4 mark then your thermostat is probably bad. This will usually lower fuel economy quite a bit.

I hope not. I think whiskeywarden is referring to the MAF/IAT sensor at the air cleaner assembly that looks like:
http://my.cardone.com/Imagesftp/74/7410113-01.jpg

This is exactly what I am looking at. Is that the wrong thing?

As for the P0128 code. I did change the thermostat from what looked like the original to a new 195 deg thermo. but the temp still only gets to 1/2 way between 1/4 and 1/2 on the temp gauge. I am a novice backyard mechanic and if I know what to do I do it but I am not great on diagnosing things.

My apologies, I forgot about the MAF sensor. I saw the word "flap" and instantly thought of the throttleplate.

The temp gauge is reading the normal operating temp so the thermostat is probably fine. FWIW our Equinox has never reached the 1/2 mark in the 3 years we've owned it - it only gets to about the 3/8 area between the 1/4 and 1/2 marks just like you described.

The engine computer compares the IAT (Intake Air Temperature) sensor reading to that of the ECTS (Engine Coolant Temp Sensor) during a cold start as part of the criteria for P0128, so if the IAT sensor part of the MAF sensor is not working it may cause a P0128. The P0100 code may be programmed to be flagged in this scenario rather than a normal IAT related code since the IAT sensor is integrated into the MAF sensor and not a separate part. The computer is unable to determine which sensor is bad because it only has the readings from these two sensors to compare to each other to use as relevant data. Since the temp gauge seems to be working fine, this means the IAT sensor is probably not working.

If all the wiring checks OK, then I'm thinking a new MAF sensor might be the fix at this point. You could pull the ECM/TCM 10A fuse for 30 seconds to clear the codes, and wait to see what comes back. However, I think the P0128 and P0100 will come back.

A new Delphi OE part costs ~$60 including shipping from RockAuto.