Problem scanning OBD for inspection....
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Professional
Joined: Aug 2007
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Problem scanning OBD for inspection....
The OBD hooked up fine but couldnt' read the pcm. I had the battery disconnected to fix my reverse light wires right before the scan so could it have caused it to not be able to read since the PCM was reset? If not what would cause it?
I've had OBD scans on this car before.
No EGR vac to manifold line and AC removed are only things I really changed....
I've had OBD scans on this car before.
No EGR vac to manifold line and AC removed are only things I really changed....
Record Breaker
Joined: Dec 2006
Posts: 1,216
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From: Baltimore, Maryland
PCM reset
If the battery has been disconnected, the pcm will not be able to be read by said scanner. The pcm must so so many (not sure the exact number) of key on/off cycles before the scanner can read it properly. Do not pull battery or the process will reset. Believe it is close to 30-50 cylces.
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Professional
Joined: Aug 2007
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Ok well I'm fixing the stuff I need tomorrow and I will do a bunch of key on-offs and get it scanned at advanced to check then take it for the inspection if its all good.
And to save a post, for the reverse lights(atx harness to mtx trans) its still purple-purple and white-white, right?
And to save a post, for the reverse lights(atx harness to mtx trans) its still purple-purple and white-white, right?
Captain
Joined: Mar 2009
Posts: 724
Likes: 1
From: Hazel Green, AL
I am not too sure about having to do all that on/off key cy (cle thing in order to read the PCM. After my rebuild, when I had everything connected and ready to go, I cranked the car, drove it around for a short while, turned it off, connected my reader, and checked for codes. That was maybe 5 cycles of on/off as I spun the motor to get the oil pressure up somewhat before trying to actually crank it. My PCM had been disconnected for about 3 months when I did this.
The reason you could not read it the first time was directly due to having the battery disconnected. The battery supplies the power for code memory retention in the PCM. This is why you can disconnect the battery for about 5-10 minutes to let the capacitors lost voltage completely and wipe out error codes and "turn off" the CEL without having a ODB-II reader/resetter.
This assumes of course that once you connect the battery - both positive and ground back up - that your PCM is not bad and will let you read it. If you still have problems reading the PCM, try several times making sure the plug is firmly connected before hitting the scan button again. If you stiill cant read it after that - the PCM is likely toasted.
The reason you could not read it the first time was directly due to having the battery disconnected. The battery supplies the power for code memory retention in the PCM. This is why you can disconnect the battery for about 5-10 minutes to let the capacitors lost voltage completely and wipe out error codes and "turn off" the CEL without having a ODB-II reader/resetter.
This assumes of course that once you connect the battery - both positive and ground back up - that your PCM is not bad and will let you read it. If you still have problems reading the PCM, try several times making sure the plug is firmly connected before hitting the scan button again. If you stiill cant read it after that - the PCM is likely toasted.