Hi, I own a 93 Trans Am LT1. I just drove 4,000 miles across country and it ran perfectly without any service engine soon lights at all.
When I got home, I drove about 6 blocks, was doing about 30, and the car shut off instantly (but the radio stayed on). In about 2 seconds it came back on and no misses or anything, ran great. Then I went about 4 more blocks and it quit again with no other warnings. I restarted it, it fired right up and I drove home running strong.

When I got home, I checked the error codes and had three errors:
- 16 - Distributor ignition system, low resolution signal -circuit malfunction. Cause: Wiring, distributor, ECM
- 28 - Engine control module (EGM). quad driver/ output driver -circuit malfunction. - Cause: Wiring, ECM controlled components. ECM 1:1.
- 32 - Exhaust gas recirculation (EGR) solenoid. - Cause: Wiring, poor connections, EGR valve, ECM.

To me this sounds like maybe a bad wire -> a bad EGR or less likely a bad ECM. I would love to hear from anyone with knowledge as to what I should check first and any intelligent feedback anyone may have as to my best options to resolve this.

Thanks

 

HI, I have another 93 trans am so I swapped out the ICM's (Ignition control modules), the TA with the issue had a Singapore GM ICM which I removed. I cleared the error codes, swapped in an OEM American ICM from my other TA and fired right up. I drove 2 miles to a gas station and it died. I coasted into the pumps, filled it up with 93 octane and drove home uneventfully. When I got home, I checked the error code from when it died and it gave me the code 16 -->
- 16 - Distributor ignition system, low resolution signal -circuit malfunction. Cause: Wiring, distributor, ECM
I am going to see if possibly there is a wire issue next. All or any bright ideas are most welcome. I need this car running. Help!

 

I have a 93 as well. You might try a new opti wiring harness, or at the least removing yours and inspecting it for breaks, exposure or corrosion at the terminals.

Hopefully it's that, but all is not lost If it is the opti. Chances are it's dirty and gunned up. If you have a Delco GM opti it can be cleaned and released and run like new. Also I find the early optis easier to install. Spline drive. Good luck and report back.

 

Thx F14D. I will do that next.

Tonight, I took it back out again. I went about 10 miles. 3 different stops and it ran strong all the way with no codes. I got that 16 code when I first drove it after installing the ICM out of my other TA. That one is a GM OEM one made in USA. The one I took out was a GM one made in Singapore. I am hoping, possibly, that my ECM took a couple of miles to reset and adjust after I replaced the ICM. I will follow up either way. Thanks so much for your input.

PS --> If you are ever looking for 93 TA hard to find parts, I may be a source to check when all else fails. I have two of them and boxes of all kinds of high quality, used, OEM stuff I might part with.

 

I'll keep you in mind. Right now I am looking for engine bay fuel lines.

 

Hi, I am following up on my post. I found a vacuum leak to my egr valve. I assume that iswhere the - 32 - Exhaust gas recirculation (EGR) solenoid. - Cause: Wiring, poor connections, EGR valve, ECM error code originated.
I replaced the hose and my vehicle has not stalled or given me any error codes since replacing the leaky hose to my EGR valve. If it acts up again, I will edit this post to reflect that. If not, consider this issue resolved.

 

When ever you see a code 16 it's always the opti

 

Wire harness corrosion for my code 16.

 

The code 16 I had was a few weeks ago. After I cleared the codes, last week, only one code has reappeared --> Code 28. After I found a vacuum leak and fixed it, I haven't gotten any new codes. However, I ran up to the store tonight and when I came out it wouldn't start. I moved my steering wheel up to the highest setting and retried the key. It started right up and came home. I didn't get any error codes however it appears to lose all spark, all at once and then come back cleanly, all at once. I am not getting any misses or coughs or stutters at all, along the way. It is on and then in a flash it is off. Anyway I guess this is not resolved. Figures, that I couldn't get lucky.
That being said, this is all I have done so far to get nowhere:
- Swapped out my ICM from my other LT! and no effect. ICM is good.
- Checked all of my vacuum lines. Fixed issue with leak. No longer getting code 28.
- Pull all of my relays, bench tested them and they all click and work properly.
- Checked all of my fuses and all are good.
Tomorrow I am going to check all of my plug and distributer wires.
Stay tuned.

 

HI, I am back. I still have not figured out why my 93 TA Lt1 keeps dying on me. Thus far I have replaced the ICM with one off my other TA, I have checked just about every connection on my car, tested my relays and still have no clue what is going on. I even thought maybe it is in the steering column.
It has been almost a month since I have gotten any error codes at all. The car runs like a raped ape and then all at once just stops. All the dash lights stay on, the radio stays on and it never misses, no coughing, no sign whatsoever and no error codes, it just kills instantly. I put it in neutral, coast to the side of the road, shut off the key. Wait for a minute or two and it starts right up and acts 100% again. Then another 2 or 3 miles down the road, exact same thing.
I could use some insight. I hate to buy parts, just to find out it wasn't that part. I watched a video on YouTube the other day where a guy replaced his ICM. not the problem. Then replaced his coil. Not the problem. Then replaced the Opti-spark distributer. Not the problem. That is a heck of a lot of work to get nowhere. I don't want to follow that path.
Thanks

 

I found the problem. It was a bad coil. It is not always the opti-spark. $30.00 and back on the road. Diligence pays off.

 

That was short lived. It died again. I replaced the optispark and it fired right up. It purrs now

 

oct 9 i said its the opti

 

Bad opti-spark distributer. Replaced and works great. I also put my primary cooling fan on a SPST toggle switch under the steering column to the left of the OBD1 port. That solved all of my cooling issues as well. I put a 180 thermostat in it, when I did the opti-spark. I replaced all of the hoses and kept the old ones in a box for emergencies.
This thread can be marked as resolved. Thanks all for your input. Beav

 

Yes, you were right. Bad opti-spark distributer. Replaced and works great. I also put my primary cooling fan on SPST switch under the steering column to the left of the OBD1 port. That solved all of my cooling issues as well. I put a 180 thermostat in it, when I did the opti-spark. I replaced all of the hoses and kept the old ones in a box for emergencies.
This thread can be marked as resolved. Thanks all for your input. Beav