Holden / Pontiac TCM Checksum errors

[bK]

I've just started working on a VZ Clubsport LS2, T42. Just got thrown by this error message which I've never seen before tuning with Flashscan. Going through the normal procedures > IGINTION ON > click READ CALIBRATION DATA > select T42 CONTROLLER > click CHECK STATUS (result OK) > click START.

Once Flashscan has completed reading the T42 and after the 15 seconds countdown has finished, this message appears:
http://nqhsvls-1.com.au/efilive/t42-checksum.jpg


Looking in EFILive tune screen you can see the checksum errors:
http://nqhsvls-1.com.au/efilive/t42-tune.jpg


So I click on the UPDATE CHECKSUMS and get this lovely message:
http://nqhsvls-1.com.au/efilive/t42-warning.jpg

I've read the PLEASE NOTE and sounds exactly right for my situation but not seeing this error before and not seeing any mention on the forum I thought I would post to ensure it's fine for me to UPDATE CHECKSUMS.

Cheers,
Brett

[Blacky]

The Holden T42 calibrations checksums are wrong from the factory - we don't know why.
Yes it is fine to correct them, in fact you MUST correct them or EFILive won't let you flash the TCM.

Regards
Paul

[ScarabEpic22]

Another instance of GM being weird, huh?:bash:

[bK]

Thanks for that, I was 99.9% sure that was the case.

[Tre-Cool]

Someone needs to run a spell checker through those bits of the code me thinks.

DO NOT PRECEDED WITH OPERATION.

incorrect and/or disbaled checksums.

:lol:

[Blacky]

Someone needs to run a spell checker through those bits of the code me thinks.

DO NOT PRECEDED WITH OPERATION.

incorrect and/or disbaled checksums.

:lol:

Doh!

[GMPX]

Wow Paul, when did you type that one up?, 3am after some Jack and Coke?

Cheers,
Ross

[Blacky]

Wow Paul, when did you type that one up?, 3am after some Jack and Coke?

Cheers,
Ross

I'm beginning to wonder... But you know what they say, you can program or you can spell, but you can't do both.:bash:

[GMPX]

You don't need to know how to spell to program CPU's, but nothing is written in English anyway. People in the 'real world' just don't get it when you get change from a shop and you complain about a divide by zero error.

Cheers,
Ross

[LT1WIRING]

does the checksum really matter? I just did a 99 vette tuned by a known tuner a few years ago and they disabled the checksum because they rewrote a 411 to run non DBW. I actually had to read it with other software and force a 896 file into it before efilive would even get past the bootloader. efilive kept telling me the bootloader was locked but it was'nt. now the pcm is happy. one thing that did come out of it was every time the battery went dead the car would not start until it was sent to the tuner that origonally tampered with the pcm. so the question will an incorrect checksum stop a car from running?
Dana

[Blacky]

does the checksum really matter? .... so the question will an incorrect checksum stop a car from running?
Dana
Yes a bad checksum*** can (and usually does) stop the car from running. That is the whole point of the checksum. It is the PCM's way of determining if it is "brain damaged". If the checksum is bad then some or all of the data in the PCM is corrupt. In that case the PCM has no way of knowing if any of its calculations are correct. Usually it puts the PCM into limp mode and/or won't let the engine start.

Normally if a tuner deliberately chooses not to correct the checksum after modifying the PCM, (usually because they don't know how or do not have the tools to generate a new checksum) then the tuner will disable the checksum. That means the PCM will ignore that the checksum does not match the data in the PCM. It also means that the PCM will never detect any faulty/failing memory. So strange and weird errors can occur and the PCM will never detect them. You could end up chasing phantom problems for weeks or months in that case.

*** Technically it is not the checksum that is bad - but the data that is being checksummed that is bad/corrupt. If you *know* that the data in the PCM is correct, then using EFILive you can regenerate a checksum for that data. EFILive will not let you flash the PCM if the checksums are incorrect.

Regards
Paul

[GMPX]

See also -
http://forum.efilive.com/showthread.php?t=7870