my friend gave me his obd1 gsr ecu to fix. the ecu is throwing cel for code 15 (Igntion Output signal). i wanna know what part of the ecu controls this. pin A21 is for the ICM so im gonna check all the devices that are connected throw pin A21. Car starts up fine with my ECU so its not a engine/ignitor problem

gonna post in pgmfi.org as well