I was driving home from work last night when the service engine light went on. I pulled into my driveway and checked for codes. It flashed the 12 about four time which is annoying because it runs bad and won't give me a code. But then the light stayed off, then flickered a little then stayed on for a little bit, then flickered off. The fan turned on and off. Do I just have a bad ecm? I've had a problem with the SES light and not getting codes for a while, but it's gotten much worse recently. Any help is appreciated. It's a 1986 Trans Am 305 tpi

 

You DO realize thet the ECM will store and display a '12' if the distributor reference pulses are interrputed while the engine is running, right?

 

I just don't know why when trying to get codes the SES light flickers irradically. I know there is one flash, a pause, then two flashes, a pause, and it's supposed to do that. The light looks like it's breaking contact though. The fan kicks on when you get codes, but when the light does this the fan turns on and off with the light. And this doesn't happen every time I drive the car. Also when the SES light does go on while driving and I turn the car off I hear the fan kick off. Which it wouldn't do since the car doesn't heat up past 190.

 

hi vader,
i;ve seen on another web page that in 1986 the 305 tpi had an optional prom to use it came later in the year
do you no anything about this new prom because i don't think my 86 got it in there thanks