04-18-08, 10:24 AM
Hey folks - looking for opinions on the following:
Each time I go WOT the SES icon (yellow engine) pops up on my 99 STS N*
Code set is PCM 0101 - "MAF sensor performance".
I swapped out the MAF sensor and the same thing still happens.
No other codes set. Occasionally when viewing the on board stats the message "does not support PCM" comes up and I have no idea if that is related.
Any opinions before I have to visit a dealer?
Phil from Ottawa
84 Buick Regal Grand National
99 Cadillac STS N*
04-18-08, 12:07 PM
Have you cleaned the TB, might help. What shape is the air filter in. K_C
04-18-08, 02:31 PM
Broken wire or connector at MAF plug ?? K_C's idea to check the air filter is good: the MAF circuit "expects" to see a certain amount of airflow at certain throttle openings. If the flow is too low or too high for the predicted air volume, a DTC will set.
04-18-08, 05:25 PM
New air filter, plugs and PCV valve in first week March.
Car runs fine if I baby it runs up to 130/140 kms/h without effort; however, if I even push it a bit the code is set and car drops into limp mode. When I review and clear codes it usually goes right back to running fine when taking it easy BUT on at least two occasions clearing codes did not get it out of limp mode right away. I needed to clear codes a couple of times.
TPS was changes about three years back.
Cleaning throttle body and checking for broken wires are good things to do, but, wouldn't a broken wire set the code right on start up; or at least some other code related to MAF?
04-18-08, 06:36 PM
What about that "does not support PCM" message? Is the sensor you swapped a GM part? K_C
04-18-08, 07:10 PM
Sometimes the trouble is cleared by replacing something as simple as a dirty air filter.
04-19-08, 10:52 AM
The PCM support message came up before I changed the MAF and as far as I know it was GM. I had been driving the car for about three years before this happened to me. The air filter is less than a month old and I don't drive on any dirt roads up here.
Still at a loss - will clean throttle and check for loose/broken wires.
04-19-08, 01:41 PM
If you have the in-line MAF unit, check the intake air piping from the MAF to the throttlebody. An air leak after the MAF will not set a lean code but will set a MAF code, which will severely reduce performance.
05-07-08, 10:09 AM
OK - had to take the car to a local used car dealer. Within a few hours I got the call that my catalytic converter was plugged up. GM Canada price for new cat - $1,600.00 as they would only sell with a new muffler.
After market cat $500.00 plus about $25.00 worth of adapter clamps etc.
Total bill $925.00 cdn
Technician swears that I have at least 5 times more horsepower than when I brought it in. As i went to our first cruise night with my Grand National, my wife drove the STS home. I will have to drive it this weekend to see for myself.
All in all it is worth the 925.00 for peace of mind - was driving me crazy.