I am amazed by the ecm. So even little things are interesting. My question is about the ses light. When the ignition first turned on(koeo) the ses light will blink hen stay on. I had another thread about this. But it was never clear on what the ecm is doing. It seems to check the prom. Cause with a bad prom the ses light doesn't blink once then stay on. It just comes on w/o a
"wink". Is the ecm looking at the proms checksum or what is going on??????

 

The SES wink means the code passed the checksum routine. No wink. IMO, means don't bother turning the key any further.

 

same here..no wink=no start....or the unsoldered prom is not seated fully

 

I ran a test today. The ses light flashed like normal. then I disconnected a sensor and ses light didn't blink....

 

So if one of the sensors is not connected the light won't blink? It just stays on all the time when jumped at the ALDL connector? Instead of giving you a code for that sensor?
thx
craig

 

The light blink is actually the ECM performing the checksum on the rom. The only time the light wont blink is if there is a major hardware failure, like a dead MPU or a rom that cant be read at all.

 

If the ECM is completely disconnected as are both IP to ECM harness connectors, should the CES light be on or off with the ignition on? According to the Assembly Manual from GM, it should be off, but mine is on, which I interpret as indicating a short to ground in the CES to computer harness. I thought the computer controlled the CES light exclusively.

Also, can anyone recommend a good replacement prom for my '86 TPI 305? I have my doubts about the PROM and would like to replace it. I live in SoCal and the car has to pass the smog check so an aftermarket PROM that is not to radical would be fine.

Thanks,