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