98 PCM Diagnostic question

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Oct 13, 2005 | 12:33 AM

HALLZ

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From: Sacramento

98 PCM Diagnostic question

What would cause the PCM to command the fp off and keep the car from firing?

A quick rundown or the situation can be found @
https://ls1tech.com/forums/fueling-injection/393904-fuel-problem-has-everyone-stumped.html

Now I am down to the PCM and was wondering if anyone could explain why the PCM went down.

DTC was PO601
Internal Control Module Memory Checksum Error

Theory's welcome!

Oct 13, 2005 | 01:14 AM

HALLZ

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From: Sacramento

BTW,
No MIL and I was wondering if a reflash would fix the code and correct the check sum error??

Thanks!

Oct 13, 2005 | 01:16 AM

SmokingWS6

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From: St. Louis MO

Is the security light blinking while trying to crank it. Perhaps its a vats issue.

I've never seen that code thrown before. Ever happen to crash the pcm while writing? 98 pcm don't like to recover quite as easily as the 99+ do.

Oct 13, 2005 | 01:30 AM

HALLZ

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I dont beleive the car was evar flashed. (but I'll ask) I will check if the light is flashing. However it does the same thing in another car. It would'nt fallow the PCM to a diffrent car would it??

Just cranks over and will not let the car start up.

Oct 13, 2005 | 06:37 AM

EFILive

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Quote:

Originally Posted by HALLZ

What would cause the PCM to command the fp off and keep the car from firing?

A quick rundown or the situation can be found @
https://ls1tech.com/forums/showthread.php?t=393904

Now I am down to the PCM and was wondering if anyone could explain why the PCM went down.

DTC was PO601
Internal Control Module Memory Checksum Error

Theory's welcome!

We (at EFILive) have tripped over that DTC a few times during some "extreme stress testing" and that DTC has been nicknamed the "nasty flag". Pretty much your PCM has decided that something is seriously wrong and its time for a new one. The PCM most likely cannot be reflashed* (and should not be reflashed) since the memory has failed.

* I presume it is for safety/legal reasons that once a PCM has failed a memory checksum or other serious fault, the PCM deliberately prevents itself from being reflashed. Short of removing the chip and reflashing it manually there is not much you can do.
If you have not ever tried reflashing the PCM and you got that fault, then chances are the PCM's memory is really damaged and the PCM *must* be replaced.

Do you have a spare PCM you can test with?

Note: what I described is just one possibility, there may be other reasons for the symptoms you are seeing.

Regards
Paul

Oct 13, 2005 | 09:25 AM

slow

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From: Orlando

if you flash a file, and the checksum is corrupt, the pcm is toast.

I was able to flash the pcm fine, it would just not start the vehicle, I don't remember if it was a 601, or 602 error.

Ryan

Oct 13, 2005 | 09:34 AM

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From: Knoxville, TN.

Yep, once that Checksum error has been set at least on the '98's , your PCM is toast. I sent and tried to have mine "recovered", and it did not help.
All you can do is trash it, and get another one.
Make sure you match up the GM service numbers, etc. on the tag on the PCM, and be sure to get one for the correct tranny (a4 or M6) and ONLY '98 PCM's will work for a '98 !