I am getting a code 43 which is the ESC module I think. Does my car have a seperate module or is it the ECM? I recently installed the MSD 6a could this have anything to do with it? I dont think it does but I replaced everything except the ignition module and the distributor when i rebuilt the motor. Also I keep getting a code 23 for the MAT sensor which I have already replaced the sensor once already. Car gets a little sluggish sometimes when the SES light comes on and I try to launch it.
Thanks, Gary

 

In 1990 they eliminated the separate ESC module, so your Knock Sensor is connected directly to the ECM. (Dk Blue Wire)

I'm not 100% sure what would set the code on a vehicle without the separate ESC module, but on cars with the ESC module the ECM has to see a low voltage (which indicates knock) for more than 5 seconds straight, and/or the circuit fails the functional check.

With your 1990 there's really only so much it could be. It could be the sensor, the wiring, or the ECM. (or you have alot of knock )


A code 23 will set if the MAT sensor indicates a temperature below -22 degF for more than 12 seconds if the engine has been running for more than a minute and hasn't moved yet. An open circuit or sensor will also set a code 23.

The Mat sensor basically lets the ECM calculate changes based on air density (colder air = more dense) If your sensor is going bad and telling the ECM it's colder than it really is then it will try to run richer and will be more evident as the engine warms up. Since you already replaced it once it's unlikely that it's the sensor (unless you got it at Autozone) I would check connections first, but it could maybe be the ECM. If you know anybody with a scan tool you could check to see what temperature the ECM is being fed by the sensor and compare it to resistance readings at the sensor itself. The higher the temperature, the lower the resistance.

 

Thanks Cooper i will have to check my knock sensor. I have Moates software so how many knocks will set off the SES light. I will have to check and see what i am getting there.
Gary

 

I don't think it's the number of knocks that sets off the SES light, rather if it sees too low a voltage for too long. Obviously there's no such thing as a single continuous 10 second knock, so the ECM knows something in the sensor/wiring itself isn't quite right.