Lately my car has been acting up, and was wondering if you guys could help. The problem I'm having is when i give it steady gas the rpms bounce back and forth (mainly between 1500-2000rpm). This happens while driving and in park. Another thing i noticed is that the OBD2 scanner rarely ever connects. Can this mean that i have a bad ECU or is it something else? Besides this, the car idles perfect and has good power.
Things i already replaced:
engine wiring harness
cleaned MAF sensor and throttle body
vacuum lines look ok, and seems to have no leaks
Last edited by greasemonkeyjoe; 10-18-2012 at 06:45 AM.
I looked for a way of testing the OVP relay but could not find any specifications for this part. I would just replace as very cheap. I think this relay also delays power up the Diagnostic module and MAF until car is running. Not 100% about this though. I took cover off mine and noted there are three relays and some electronic devices. I suspect this was the problem with mine, as OVP was immediately powering up the Diagnostic module which caused the firmware to crash. Then I could never get the ODB II readiness monitor to go to ready no matter how many drive cycles went thru. As a matter of fact my ODB II scanner read "unavailable" on the readiness monitors. After OVP replacement, disconnected battery, did a ECM reset/re-learn procedure and drove for about 200 miles. Finally go 4/6 readiness monitor to pass which passed emissions here in UT.
Do you have a ODB II reader?
Reason ask about ABS is this module is also powered by OVP.
Check you MAF is working, no 0101 or 0170 codes.
My SRS light has always come on for about 1-2 minutes after starting the engine but always (knock on wood) shuts off. Need STAR diagnostics to get codes, I think?
I have an actron obd2 scanner. I will try and see if i can buy a new ovp relay today. I tested the MAF by disconnecting it and seeing if the problem persists, and it does. The rpms still fluctuate so i suspect there isnt a problem with the MAF, but i may be wrong. Also when i disconnected it, the car went to stall.
Last edited by greasemonkeyjoe; 10-19-2012 at 06:58 AM.
Try swapping out the OVP relay and see if you can get diagnostic mode working. That way you can check for OBDII codes.
You can build a LED blink code reader to access the blink codes directly from the ECM using the 38-pin diagnostic connector. This will allow you to get codes without the using the diagnostic module.
After you replaced the wiring harness did you do a ECM re-set/relean procedure? I found that I had to do this to get the throttle actuator working after I repaired my wiring harness. Also disconnected my battery to reset the diagnostic module. I see you replaced your wiring harness.
Finally got information. To reset the ECM follow the attached procedure. You have to make sure the OBDII codes are all cleared or the procedure will not work. I have also attached a schematic of the pulse code reader which you can use to clear codes or use your OBD II code reader to clear the codes. Once you have codes cleared follow the resetting and reactivating ECM memory procedure. This will reset the ECM and will re-learn the throttle actuator position.
You might want to disconnect the battery to reset the diag module.
Give that a try to see if Throttle actuator starts working. Make sure you don't have another vacuum leak.
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