I tried to read the error codes from my car, an 82 Firebird V6. There was no Check Engine light coming on in the dash. I found that the bulb had been removed, Suspect!. I replaced the bulb and now that remains on all the time. When I short pins A and B on the ALCL connector on the driver side nothing happens. The bulb stays on. On the 82's there is a remote lamp driver circuit near the ECM so I checked that and is working fine. I next checked the ECM connectors to make sure the signal from the ALCL connector was getting to the ECM and it was, shorted A and B and the ground was on pin 5 I think it was. I grounded the pin from the ECM harness to the remote lamp driver (pin G) and the check engine light went off so all that is working fine. So I taught the ECM was faulty and I bought a remanufactured one and tried that. The same thing!. I was not happy.

I looked at my service manual again in the hope for some answers. I decided to check as many pins on the ECM harnesses as I could. I checked the grounds and they are fine. I checked that the 12V from the ignition is getting to the ECM and it is. I checked the 12V continuous (memory, Pin R) and nothing. I followed the wire to the pigtail beside the battery and someone had grounded it to the body so no power on that pin. This really confuses me,

if there is no 12V continuous (memory) does that mean that the ECM has no power.
If the ECM has no power then the car should only work on limp home mode (so I am told) and not drive properly but it does.
Will the car under any circumstance run without ECM working.
Does the 12V from the ignition when the key is turned to run power the ECM also or is that just to sense when the dash lights are on or the car started.

Can anyone help, Confussed!

 

An '82 would have a computer controlled carb & distributor. So it will run without an ECM (could unplug it and the engine would still run).

In the EFI ECMs the +12 volt battery power does power the ECM. With the ignition switched +12 volts signaling the ECM to power up/down.

RBob.

 

Will the car drive okay if the ECM unpluged, what about the "limp home mode" if the ECM fails. At the moment the car drives fine. 60MPH no problem and doesn't seem too bad on Gas. Are the M/C solenoid and distributor controlled from the ECM and does it take readings from the oxygen sensor to control the pulses to the M/C . (was reading this stuff last night).

Thanks.

 

The ECM does control the MCS via feed back from the O2 sensor. Odds are that the ECM also controls the distributor. Would need to look at it to verify this. Most distributor ICMs have advance built in when not under ECM control.

Can check that with a timing light.

RBob.

 

There is a 4 wire harness going to the the Distributor so it must be under some type of control from the ECM. Will connect up the 12V continuous (memory) wire to the ECM and see what happens.

Thanks.