PROM chip questions... new to forum

[timpage]

Hi all. I found this forum researching some quirks on my '88 GMC K1500 (350 and manual 4 speed).

Ive been researching why my speedometer is innacurate and shift light stays on under most driving conditions. To the best of my research this truck is on its second engine (current appears to be GM Goodwrench replacement 350 with all original style TBI components) and had a TBI 350 factory. MDO codes confirm this truck has what appears to be its original manual 4 speed transmission, and near as I can tell has original axle gearing (I believe 3.73 ratio).

For the heck of it, I pulled the PROM chip cover off the ECM, and found that the chip has a AMUR 0055 code. Has what appears to be the correct 1227747 computer. From what I found, the AMUR PROM chip is for an '87 model year GM with a 350 and an automatic, not a 1988 model year 4 speed manual truck such as mine.

My only complaints are innacurate speedo and the shift light at this point... truck otherwise runs well. Will this PROM chip cause these issues (and any other issues I'm not noticing?)... and what options do I have to correct/change the chip if it is the right thing to do?

Hope this is clearer than mud lol... thanks for any input.

Tim

[jim_in_dorris]

Tim your best bet is the ASDX bin which is for an 88 tbi truck with manual transmission

[timpage]

Thanks for the reply! Are there places that sell factory PROM chips?

[timpage]

Or, after understanding a bit more on the site here and how many of the folks here burn their own chips... is there anyone willing to program a chip to ASDX bin specs? For a fee of course... lol?

[timpage]

It also just occurred to me that, after looking at the ECM tag again in my GMC, it may have been swapped at some point in its history (I bought the truck in January 2016, so 4 months). Though the ECM is a 1227747 ECM, the AMUR PROM chip is matched to this particular ECM. I tried to post a picture to this but am not sure how too. So is a simple PROM chip change the cure or do both chips in the ECM need to be changed (ie. a matched set)?

[Dr_Grip]

You only need a new PROM chip. The second chip is identical on all 7747.

[timpage]

Thanks for the clarification!

[damanx]

Sent you a PM about burning a prom.

[damanx]

Any updates on the chips I sent you?

[timpage]

The tracking number shows for a tomorrow delivery so I'll keep you in the loop. Thanks for checking in

[damanx]

Oh that sucks. Hopefully the post office has it.

[Six_Shooter]

You only need a new PROM chip. The second chip is identical on all 7747.

Not true. The small chip is known as the NETRES, and is what sets up Limp Home Mode, and hardware cylinder select. At the very least they are different between 8 cyl and 6 cyl applications.

[jim_in_dorris]

Not true. The small chip is known as the NETRES, and is what sets up Limp Home Mode, and hardware cylinder select. At the very least they are different between 8 cyl and 6 cyl applications.

The AMUR bin is from a G van 5.7l auto, so the netre really should be good. You of course are correct about the 6 and 8 cyl. Netres being different, but in this particular case he should be okay

[Six_Shooter]

The AMUR bin is from a G van 5.7l auto, so the netre really should be good. You of course are correct about the 6 and 8 cyl. Netres being different, but in this particular case he should be okay

Right, I'm just pointing out the fact that the statement made is incorrect or at the very least misleading, especially to someone just learning about GM EFI tuning and hardware swapping. ;)

I'm sure if we dug deep enough we'd likely find that not even all 8 cyl NETRES are the same, because even in LHM, a 305 is going to need a different amount of fuel than a 454... Just like it is with other ECMs, which I have found out the hard way... lol