1227747 & 1228747 ECM Differences?

I'm new to TBI and am troubleshooting an RV I bought. The ECM set Code 51 (ECM/PROM problem). I removed it and found a remanufactured 1227747 ECM with an AUMZ PROM inside. In BCC lookup.xls this PROM is listed as being used in the 1228747 ECM.

"Hack job" things have been done to the RV and it's had very poor maintenance and I don't trust anything I find. No info from previous owners is available.

I compared 7747 & 8747 ECM wiring diagrams and the wiring connections look the same. So externally they're the same, but there must be some internal differences other than the PROMs/respaks.

Anybody have an idea what the differences might be?

Anybody tried substituting one ECM for the other (keeping same PROM)? What were the results?

-Doug

the ecm's wire the same, but the proms will not interchange the ecm uses a different mask on the bin files in the proms.

1228747 information: http://www.gearhead-efi.com/Fuel-Inj...Information-4F

1227747 information: http://www.gearhead-efi.com/Fuel-Inj...Information-42

dave w

They are the same hardware, but they have some code stored internally besides the prom chip you access under the cover. This internal code is different which doesn't allow you to swap the prom between the two. The internal code addresses the prom in different locations.

Thank you all for the info. This would explain error code 51...

I picked up an 8747 ECM at a junkyard yesterday. When the RV exhaust system's finished I'll try out the ECM. If the last "mechanic" damaged the PROM I'll be buying tuning & programming stuff sooner rather than later! (the bin's available here on Gearhead EFI)

-Doug

I know this is an old thread but it seems appropriate instead of starting a new one. I'm helping a friend troubleshooting his 90 454SS C1500. He has the 1228747 and I can't find the corresponding .adx file for the 4F mask. Does anyone have one?

Never mind, I found them. All I had to do was look a little further down the link @dave w posted, duh!