I get a "Service Engine Soon" Message in the DIC when coasting for 15 to 30 seconds or more (with no pressure on accelerator at all). I do NOT get a SES LIGHT in the instrument panel associated with the DIC message. If I touch the accelerator again or stop it goes away immediately. Pontiac Dealer and Independent Mechanic were unable to figure this one out.
I also get intermittent surging (visible via tachometer needle movement up and down about 100-200 rpm as well as being able to feel it) on medium grade uphills with only light pressure on the accelerator -- just enough to try to maintain speed up the hill. Not sure if this could be related.
My 2002 SSEi has about 148K miles. Both O2 Sensors and MAF have been replace due to unrelated ODBC-II codes that were thrown and successfully resolved.
Yes it was tuned up at around the 100k mark as recommended by Pontiac. The tranny and torque converter were replaced then too. The surging feels more like engine than transmission. Since the SES is a message in the DIC and not the light on the instrument panel, there are no codes. This has been checked more than once with more than one type of reader. BTW, the fuel pump and filter was replaced by a Pontiac dealer about 10K ago because it faed completely. Both problems (DIC message and surging) were there before and after that repair.