I know almost nothing of the pcm's on the cars. I have gone 2 years since a check engine light and i was wondering if it works since i had a plug wire burnt so bad the car would barely run and i thought i had a blown head gasket or worse. I unplugged the IAT and drove the car and no light came on. I figured this would trigger a light but maybe only a trouble code on the computer. Could there be a problem and what do i do to check or fix it? I have Freescan and i get all the sensors except knock so i am lost.

 

Just wanted to add this. The check engine light comes on when the key is first in to start and light goes out soon after it starts.

 

Unplug the MAF sensor, that should give you a code. The IAT shouldn't trip an error code, it just reports really cold air when it's disconnected.

 

So, what are DTCs 23 and 25 for?

 

The IAT needs a resistor to think the connect is complete and then the computer think its a cooler temperature than it is. Unplugged it sees an open circuit and should trigger a trouble code. Since i got no check engine light i guess i a scan is needed. I was looking for a dash warning light so i will try the MAF next.

 

Why don't you do it a little more scientific then just looking for a SES light?

The IAT resistance at 100 C or 212 F is approximately 177 ohms.

And at 0 C or 32 F it's approximately 9420 ohms.

Why don't you apply those resistances to the IAT harness and see what reading you get from the PCM?????

BTW for what it's worth. You know the SES comes on during initial check. You said so. There is also DTC 11 which tells you there is problem with the SES light circuit if you had a problem.

Stop worrying and leave it alone.

 

Beats me, I just know that's how my car is.

 

The code 23 came up a day later and a lot of driving. Well if thats all thats slow on my car its OK.

 

I guess GM just made up DTC 23 and 25 and put it in the codes lists to confuse people. Maybe they just like to fool us all with a bit of bad info every once in a while.

In order for the IAT codes to set:

Low voltage/high temp (short to ground):
-no active codes for MAF, CLT or VSS
-vehicle speed greater than 25 MPH
-engine run time greater than 30 seconds

High voltage/low temp (open circuit):
-no active codes for MAF, CLT or VSS
-coolant temp greater than 0*F
-air flow less than 15 gps
-vehicle speed less than 7 MPH.

 

I believe that is true of a lot of Engineers

 

To quote DOC from Back to the Future "DO YOU KNOW WHAT THIS MEANS? THIS THING DOESN'T WORK AT ALL!"

Great, that means mine is broken too