: '97 DeVille SES but no current codes?

05-17-09, 10:47 PM
The other day the SES came on on my '97 DeVille after hard acceleration.
So I checked the codes and it read PCM P0101 history, PZM B1971 history, and PCM?
1) Why are there no current codes?
2) What does PCM? mean? An option to read more codes?

Thanks to all in advance.

P.S. The car has 77k and runs very well with recent plugs and fuel filter.

05-18-09, 08:30 AM
PCM stands for Powertrain Control Module. If there are no Current codes, the fault has not repeated itself for at least 3 ignition start-warmup-run-off cycles. If the fault does not repeat after 40 cycles, the code clears entirely.

It's entirely possible that the acceleration tripped a MAF sensor flow or air/fuel mixture signal, which will set the SES. Is the light still on ?? try a few more strong accelerations and see if the light sets again. It may indicate a need for MAF or throttlebody cleaning. Also, EGR cleaning. Many, many posts on these methods. (PCM 0101 is a MAF sensor code. Clean it with TB cleaner, rags, and a toothbrush. Be VERY careful of the tiny heated resistors on the wire bridges. DO NOT dent or distort the honeycomb flow straightener.)

In your code reading DIC sequence you may have seen a PCM ? request for module number. Sometimes the module type or serial number is mistaken for a DTC.

Go back through the "How to pull codes" at the top of the main page and scroll through some of the various OBD-II codes to learn what the different module acronyms are.