Cadillac Repair: 1992 Cadillac Sedan Deville, cadillac sedan deville, code definitions

Question
Hello,

I have a 1992 Deville with a 1993 4.9 engine. The original engine was a 92 4.9. I drove the car for two years after the engine change with no problems. My mileage dropped from 29 to 16 on long distances.  My local mileage is around 14 to 16.  I had the car worked on by a local mechanic and he was not successful.  I also had a strong fuel smell when stopping at a light or stop sign.  He changed the vacuum canister, removed the fuel rail,and numerous other things. No luck.   I don't believe he checked the codes.  I checked them using the procedures you outlined (thanks very nice instructions) and received the following codes.   E.12 no spark reference from ignition module or distributor.
E.38  I think this is  IAT or Map  circuit sensor open
E.52  my understanding is that says the computer has been reset
I called the local parts store for code definitions.
The car runs fairly well, a little rough idle and when you allow it to idle down and hit the throttle there is a slight hesitation.  Any assistance you could give me would be greatly appreciated.  


Thank You
Jim Haffly

Answer
E38 is an open MAT (manifold absolute temperature) sensor fault. Located near the alternator and the cruise control. Buy a new one so you will see what your looking for.

After installation, CLEAR all the codes from the computer and see which codes come back.