I'm probably asking a question that no one can answer but here goes. Does anyone know the difference between a 1983 Pontiac GP ECM and a 1984 Pontiac GP ECM. I have both and they do have different part numbers on them. They are both form vehicles that have the 305 4 bbl in them. The 84 ECM I think is bad so I am using the 83 ECM. I am getting a code 41 which is related to the ignition module. But the distributor is new and it made me think that the ECM might be why. Here is something I found on RepairPro.com
"GM OBD Trouble Code 41
Ignition Control Error
The ECM monitors the ignition module performance. Code 41 can set when the ignition system performance does not meet factory specifications.
Fault Code Description
41 - Ignition control error
Symptoms
Engine cranks but won't start
Engine stalling
Lack of power
Common Problems
Faulty Ignition Module
Faulty Crankshaft Position sensor
Faulty ECM or wiring issue between ECM and ignition module
MEM-CAL Error
If the ECM detects an internal fault with the MEM-CAL, code 41 will set. The MEM-CAL is a special "chip" that is installed in the ECM, based on the particular vehicle configuration.
Fault Code Description
41 - MEM-CAL error
Symptoms
Engine may not start
Engine stalling or erratic performance
Common Problems
Internal ECM or MEM-CAL fault"
I am not experiencing any of those problems (no start, stalling, lack of power, etc.) and obviously it doesn't have a crank or cam sensor but this is what peeked my interest: "The MEM-CAL is a special "chip" that is installed in the ECM, based on the particular vehicle configuration". Even though both vehicles are essentially the same, It made me wonder if something like EPA regulations might have changed between the 2 years causing a small difference in specs and calculations. I would be willing to remove the ROM chip from the 84 ECM and install it in the 83 ECM if I knew what chip that was. Even though the 84 ECM might be bad, it's pretty rare that the ROM chip in it would be bad.
"GM OBD Trouble Code 41
Ignition Control Error
The ECM monitors the ignition module performance. Code 41 can set when the ignition system performance does not meet factory specifications.
Fault Code Description
41 - Ignition control error
Symptoms
Engine cranks but won't start
Engine stalling
Lack of power
Common Problems
Faulty Ignition Module
Faulty Crankshaft Position sensor
Faulty ECM or wiring issue between ECM and ignition module
MEM-CAL Error
If the ECM detects an internal fault with the MEM-CAL, code 41 will set. The MEM-CAL is a special "chip" that is installed in the ECM, based on the particular vehicle configuration.
Fault Code Description
41 - MEM-CAL error
Symptoms
Engine may not start
Engine stalling or erratic performance
Common Problems
Internal ECM or MEM-CAL fault"
I am not experiencing any of those problems (no start, stalling, lack of power, etc.) and obviously it doesn't have a crank or cam sensor but this is what peeked my interest: "The MEM-CAL is a special "chip" that is installed in the ECM, based on the particular vehicle configuration". Even though both vehicles are essentially the same, It made me wonder if something like EPA regulations might have changed between the 2 years causing a small difference in specs and calculations. I would be willing to remove the ROM chip from the 84 ECM and install it in the 83 ECM if I knew what chip that was. Even though the 84 ECM might be bad, it's pretty rare that the ROM chip in it would be bad.