Ok, I flashed the USDM Evo 8 ecu with the 90550001 ROM. No errors in the log.
When the key is in the on position, the radiator fan is getting pulsed on and off quickly. This tells me the harness is probably wired incorrectly.
I wired the patch harness per the Evo 7 wiring specs, assuming with the Evo 7 ROM the fan signals would be on the Evo 7 pins, not the Evo 8 pins. It seems that may not be the case.
Here are the specs I used:
Disconnect Pin 87
Car Side ECU Side
32 34
34 32
20 32
21 34
8 22
22 8
Tim