How do you test the ecm on a 2.8 1989 Firebird?

 

find your ALDL connector under the dash on the drivers side.there will be 10 or so spots on this connector.you will need to jumper the top two on the right.you can use a unfolded paper clip a 12 gauge forked wire lug.autozone has a tool that they give out if you ask for one.it's just a small thin key looking tool that you plug into these spots on the ALDL connector.
after you jumper the top two spots turn your key to accessory and your check engine light will start flashing.first it will flash a code 12,which is the ECM's way of letting you know that's it has ran a self check and it's working properly.it will flash once (pause) and then flash twice.it should do that three times and then go on to a trouble code (if you have any) that has been stored.for example a code 34 would be three quick flashes (pause) and then four quick flashes,it'll do that three times with a long pause in between each one.

 

Used to be a procedure to test the quad drivers in the early ECMs but I don't think anyone can really test computers today without specialized equipment.

 

So a Code 12 will show it's working properly ? Reason I'm asking is because I'm now getting a Code 42.

Actually I would get a Code 54 as well but I managed to bypass that one.

 

yes, that's about the only way...

 

Damn it, and I am getting a Code 12 and Code 42 *lol* plus bypassed Code 54.


Hmmmm looks like I may need to invest in some new connectors and possibly one relay when I get back.

 

code 12 is gonna be there, regardless. it will flash first, then other codes (42, for example) then 12 again. if the only one that flashes is 12, then it's "assumed" it's all working correctly. probably only way to really tell is with a scanner.

 

Yup that's what I was wondering about. If Code 12 is a guarantee that one's ECM is good to go, or if the ECM could still be bad.

 

As far as I know the code 12 only indicates the ECM is in the diagnostic mode, not actually a test of the computer. Used to see this called a "handshake code."

 

A '12' is actually an error/trouble code. It is generated when the ignition is on but no distributor reference pulses are being generated. If everything is connected correctly, that's what happens when the engine isn't running. AFAIK, only the Ford EEC systems actually had a "status" code that indicated the system is O.K. GM/Delphi systems use the SES lamp "bounce" to indicate a successful POST and diagnostic. You don't even need to scan for that one.

EDIT: I was mistaken. Ford and Chrysler had codes to indicate the diagnostic mode status. Ford had an '11' to indicate the diagnostic mode enabled, while Chrysler had a 55 and 88 to indicate the end and start of the diagnostic routine, respectively.

 

Incidentally, if you've set the base timing recently, the '42' may be present from disconnecting the EST bypass connector. That's normal. If not, you may have a problem with the ESC, ignition module, knock sensor, or a wiring problem between them.

 

I set the timing a few months back. This all happened after wiring into the fuel pump relay's green/white wire .. and then the Code 42 happened when I swapped out connectors and spliced in an used junkyard connector