OK, I've been fighting a check engine light on the 83TA that won't report a code. It's a carb'ed 305 auto for those who don't know. Checked all kinds of things, and then finally pulled the instrument panel - and one of the harness connectors on the back of the panel had a bad connection. Fixed that, and the light went out. For a couple of days. Now it's back on.

I've tried reading the codes, but it won't show any codes - not even the "12" that indicates the ECM is working properly and sees all it's sensors.

Has anybody got any ideas on what to look for or try? I'm pulling what little hair I have left out over this thing. I can't afford to lose much more hair, either! Any ideas would be appreciated since the MAP/S_AUJP/Speed Density systems are more my forte......

And I've done the search, read thru eleven pages of results to no avail.

 

How did you go about pulling the trouble codes?

You may have an ALDL problem. Pretty rare, I'd have to admit. But, perhaps something was damaged when something else was being worked on/modified.

 

I've tried it using both a "code reader" (OBD1) as well as a jumper wire between the top two pins on the right hand corner. The check engine light just stays on solid, no codes are being displayed. I'm baffled!

 

It would be interesting to see what would happen with a scan tool like Auto Xray.

It's probably worth another look at the wiring behind the cluster. Any idea what happened to cause the first wiring problem?

 

Absolutely none.

Installed the correct oil pressure sender and the gauge works fine now.

UPDATE - Bought a new reman ECM, plugged it in and the CEL is still on. And now the choke light is on as well. WIll swap back to the original ECM tonight and see if the choke light goes out. If it does, will be getting another "new" ECM. Then I'll start tracing down the wiring harness for the CEL. If it works like my '91, then the ECM is providing ground when it wants it on and a simple short in that wire would turn the light on all the time as well.

I talked to the original owner about the CEL - it's been on like that for 3 or 4 years. They had it in a shop that coukdn't figure it out either so no one has really tried running it down much from the sound of it. I intend to "fix" it or else die trying.....

 

To the best of my recollection, the CEL is wired such as to stay on when the ECM loses power. I can't confirm that now with the diagrams I have but they do show the CES light lead coming from the 'G' terminal of the ECM, a white/dark green wire. I'm thinking this terminal is normally grounded and closes the circuit to the light when the ecm loses power. I'll be able to confirm that when I get back to where my car is on Monday. If you're still working this?

 

sounds liek the problem i had and still have lol check engine light was always on and wouldnt code to save my life looked at the fuse box idiot before me forgot to put a fuse into the ecm slot thats why the light was on constantly

 

NAF - thanks for that info - yeah, I'm still trying to figure this one out. Any ideas or help is appreciated!!!

Jordo - I'll check that fuse box tomorrow! Never thought of that one.....

 

I'd think lose wiring/bad circuit between the CES and the terminal on the ecm.
Sounds like you've already run across a few wiring gremlins.

You could perhaps jump that terminal with a test light to verify. The test light should be lit with ignition on/engine off and should blink your codes when the A&B terminals on the ALDL is grounded. This is assuming that the ecm is getting proper power and the wiring issues are between it and the CES...since the PO drove it for a few years like this, that'd be most likely IMO. 'Course the lack of codes from a reader scares me...

This thing run fine and all that? New project car for you?