Anyone know much about the 80s GM computers / ECM 86 Firebird 2.8 T5 I cannot pull trouble codes, the default code 12 will not even flash. I know how to pull codes have done it before but it just stays lite. pulled ecm from under dash, wiggled all the wires n checked connection there and under hood. Sometimes starts funny and if I can get the rpms over 2000 playing with the gas pedal it sort of fixes itself and it will idle fine for a few, then for no reason starts to sputter and die if you don't give it gas and rev it up again. Can sort off still drive it but when it acts funny it like loses half power. Will back fire through the intake sometimes as I try to get ti rev'ed up on a start. Hate to start replacing parts for no reason. I know its not fuel pump and stuff, all been replaced recentaly. Now it had done that in the past, say dozen times a year but all I would do is shut the car off and coast for a bit, dump clutch and fire it back up and it would be fine. Always seemed if I turned the key on and off 2-3 times before I started it, it would keep it from doing that. And never did it once it was warm or had been driven. But now I can't make it go away doing them two things.
If I could build ones of these without paying $50 for a pre made one I could use my laptop Im told to gather data even if it won't spit out the codes its self. Though my brain isn't made for such work. Though probably super simple. I would only need it for aldl mode. see file, told 2nd diagram is the one to use. http://viragotechforum.com/phpBB/download.php?id=7438
Well, if you do manage to get codes, I have the flow charts for them. Ive got a set of GM Expert-tech books I bought from GM way back when. My Turbo car never broke so I never used them!
Not to ask a dumb qustion, but you are connecting the A & B pins together right. Should be the two on the upper row all the way to the right if my memory serves me.
Oh yea I know how to do it right. Have done it in the past though the codes were never helpful in finding other problem. Probably wont be this time either If the computer was shot id think it wouldn't run at all. Dunno really, though hoped the codes might of given some type of clue. Worse comes to worse I toss a regular dizzy and a carb on it. Though it does run great on the MPFI system.
Can you get another ECU from the boneyard or borrow one somewhere to swap our for a test??- I'd think an old one like that'd be pretty cheap at the yard- and chances are real good it'd work just fine ( the used ecu ) Robert.
check for power on pin b on the aldl should be 12 volts and pin a should be ground if not start tracing wires back to find your open or shorted wire
Ill check that tomorrow, id run out now but the battery is unhooked. Only thing I had touched before it did this was the MAF and the air temp sensor, MAF was not unhooked just moved around, air temp sensor in the intake was unplugged in and out a few times.
Well I have gotten no where, did check fuses. checking the juice between a/b shows 5 volts I built the cable using this one http://viragotechforum.com/phpBB/files/aldl_adap.jpg I get nothing from the aldl program, Still starts funny but give it some gas and it idles n revs up fine now.
rockauto to the rescue maybe, looking up a reman ECM $72 they got a list of PDF files including a service bulletin on things to check first. Constant or Intermittent Engine Light w/No Codes Stored (GM), Stalling w/No Codes Set (All Makes), Check Engine Light Goes Out When Assessing Codes (GM), Various Drivability Problems (All Makes) http://www.cardone.com/english/club/Products/ELECTRONICS/Protech/Tech_Bulletins/PT 77-0008.pdf Also the feature of the reman ECM they sell are as followed. "Original quad drivers that are not short-protected are removed and replaced with short-protected quad drivers. - Corrects an O.E. design flaw and allows vehicle owner to replace a solenoid instead of the entire ECM the next time a short occurs." As the car did have a code 33, 54 all its life. Which is FP, FP relay, oil switch, open or short circuit, defective ECM. poor connection, open or short circuit, bad MAF or defective ECM And since it has ran great its whole life I have totally ignored them codes as trying to fix them by replacing parts cept the ECM didn't help any. And chalked it up the a dumb 80s computer.
Might be getting somewhere trace wires for the MAF to the MAF relay and its connector looks like crap, touch it just a little and the big brown wire going to it just fell out.
Look over these two threads plz http://www.thirdgen.org/techboard/dfi-ecm/519271-cant-pull-trouble-codes.html http://www.thirdgen.org/techboard/tech-general-engine/519656-ever-done-resistance-ecm.html I need solid info before replacing parts. As right now IM loking at around $200 in part I have no idea if it will fix anything. [ECM, Prom, MAF, IAT] Could spend the same or less to just go to a carb n regular dizzy that I know will have it running right.
Its Alive!!!!!! Thank the lord. The ECM replacement was a total shot in the dark. Did have a few hiccups at first. Had to wire my fuel pump back up as it was on a switch. [Computer turning it on should of been a clue] I was then able to get the 2nd ALDL cable I built working and was able to do some data logging.
