Code 15 with new CTS and erradic idle - Third Generation F-Body Message Boards

89gta22 · 08-19-2009, 11:00 AM

Ok so, ive been struggling with this/these issue(s) for about a 5 months now and need and some guidance.

For starters my check engine light has been on for 5 months and is reading a diagnostic code 15, faulty CTS or ECM. I replaced the sensor about 2 months ago, cleared the codes, and within a few minutes of driving the light was back on again. After some research and tooling around with a voltmeter, i determined that the new sensor was working just fine and that apparently Code 15 can also flash when the ECM is failing. I figued i'd leave it alone until i had more time to diagnose the problem.
However, i have also been dealing with an erratic idle issue. The Idle jumps around 500 and 800 RPMs when im sitting in idle or when i stop at a traffic light, and will stall if i dont feather the gas. From my understanding, this is a textbook IACV issue. I pulled the IAC cleaned it, reainstalled it and the problem was still there. Pulled it again, and turned the ignition on to see if the probe moved and was surprised to find that it did not.

Now i would normally just go buy and IAC but im starting to think that maybe my ECM could be bad and thats the reason im having all these issues. On top of all of this, my trans mission has been running really hot, about 210 degrees when im cruising on the highway and was told that thas is often a result of the TCC not locking up (i have a 700r4), which is apparently also controlled by the ECM?

Can anyone help me out, im not really sure where to start or how to resolve this?

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tom3 · 08-26-2009, 11:48 PM

For mulitple issues like this I'd check the grounding connection. One on each cyl. head, at the rear down behind the engine. (on a V8) Sounds dumb but it's not that unusual for these to work loose and loose connection.