GEMS PROM question

[RichardS]

Chris posted the TSB for updating the GEMS prom here:
http://discoweb.org/forums/showthread.php?t=14753

Does anyone know how to identify the updated PROM? Is the label on the updated PROM different that the original? I'm looking at one and there is no part number on it to match up with the TSB, just says GEMS 8.3.

I have a working ECM and a junk one, both circa 1998. I have the junk one open and wonder if by chance it has the new PROM which can be put into my working ECU. I could just swap them but there's no real way to test other than waiting to see if I get a P0125 in 4 or 5 months when it gets cold again. The working ECM I have probably has the old PROM as I got a few P0125 codes last winter.

On a side note, I consider the other ECM I have to be junk since the CEL does not come on when powered up and the motor will not start. Is this correct reasoning or am I missing a step where a new ECU needs to be electronically mated to the vehicle?

 

[frickjp]

Prom should have a label on it. There should also be a paper label on the ECU. No CEL means security isn't set. May not be junk, just needs the code learned.

 

[RichardS]

Thanks for the info... The chip has a paper sticker on it that says GEMS 8.3, do you know what the updated chips have written on the sticker? The outside of the ECM has the normal label on it, same as the one that came with my 96, slightly later date code but otherwise the same. Should the ECM have another sticker indicating PROM update if it were performed?

And any options on setting security for the home mechanic? Or do I need it set via a testbook? I was hoping this ECM would be functional and I could keep it as a spare so I'm interested in trying to get it to work. But if I have to go pay for a testbook session then I'm not going to bother.

 

[RichardS]

Just noticed I made an error in the original post and I cannot edit it - I should have said both are circa 1996, not 98.

 

[96DiscoSE7]

On a side note, I consider the other ECM I have to be junk since the CEL does not come on when powered up and the motor will not start. Is this correct reasoning or am I missing a step where a new ECU needs to be electronically mated to the vehicle?

[/QUOTE]

any ECU needs to be initialized when put into another vehicle via testbook.........

 

[frickjp]

Thanks for the info... The chip has a paper sticker on it that says GEMS 8.3, do you know what the updated chips have written on the sticker? The outside of the ECM has the normal label on it, same as the one that came with my 96, slightly later date code but otherwise the same. Should the ECM have another sticker indicating PROM update if it were performed?

And any options on setting security for the home mechanic? Or do I need it set via a testbook? I was hoping this ECM would be functional and I could keep it as a spare so I'm interested in trying to get it to work. But if I have to go pay for a testbook session then I'm not going to bother.

If it were updated correctly, there should be a paper label on both. I'ts been while, but the new PROMS came with a label on them with the revision number on it. Then we put a paper label on the outside of the ECU to let others know the campaign was done. Sounds as if yours were not. A new PROM is pretty cheap, and last I knew, available. If you want to send the "non-working" ECU to me, the next time I get an older GEMS truck in, I'll set security and see if it works. At least you will know it it's any good.