'93 LT1 6 speed, all stock, 80k miles. First indication of trouble was when it just wouldn't start one morning. Couldn't pull any codes - including a "12" - by shorting the ADL terminals A & B. A helpful forum member told me about shorting terminals A & G, and I pulled a "1 = 41", a "4 = - - - ", a "7 = ERR", and a "9 = 72".

FWIW I had to replace a bad fuel pump in the middle of troubleshooting this apparent electronic problem, compounding the confusion.

Starts and runs fine most of the time now, but it has an intermittent no-start problem. When I smack the ECM it usually starts. While driving it occasionally goes into limp mode, and flashes "sys" on the dash display. Sometimes it comes back by itself, sometimes after it cools off or I smack the ECM. It's beginning to seem like it may be heat related, as the ECM feels very hot sometimes when it flakes out.

Best as I can interpret and trouble shoot it seems I might have an ECM going south as it gets hot. I don't think it's an ECM connection issue, since I've had it in and out several times. I'm not real confident about this though, since the manual says "1" relates to the CCM and "4" to the ECM - although the trouble code 41 translates to ECM issues.

I read (on the CF) that they no longer make '93 ECMs. If true, does anybody have any ideas about used, rebuilt, etc? I'd also appreciate any other suggestions or tests I could run to try to debug this problem. It is no fun not being able to drive my toy without worrying if I'll make it home. Thanks for any ideas.

 

If you tap on the ECM and the trouble goes away it sounds like you could have a bad ECM or maybe your PROM is not seated correctly. Have you tried to reseat the PROM? You're not going to have any luck getting a brand new ECM for your 93 but everyone(dealer, part stores, Summit, Ecklers, etc.) sells the remanufactured ones. Do a search on the forum for everyones opinions on which ones they like. Hope this helps.

 

Thanks for the input, SMROSS. It does sound logical that the "tapped" ECM working (sometimes) could make it look like the culprit. I was hoping somebody would have some input on those codes I'm pulling or similar experiences when THEIR ECM went TU.

GREAT news about the reman ECMs, though. I didn't know they were readily available. Sounds like my problem may be over - if my diagnosis is correct. I'm going to chase the trouble a bit further before I invest in another electronic part hoping it is the solution, then maybe finding out it wasn't (I HATE it when I do that). This one sounds like serious enough money I can't afford to blow the call.

Enjoy your weather! Many of us frequently wish we had more of your sunny, top-down days for a relaxing ride. Maybe about as often as you wish you had a new, unknown stretch of interesting road for a ride?

 

Just a note your car uses the same ECM as a 93 Camaros and it also fits 92/93 Vettes. The ECM part number is: 16159278

You should be able to find these easily in the wrecking yards for about $50 or less.

 

New (reman) ECM in hand - will find out tonight if I'm smart, or just poor. Local Chevy dealer gave me a $20 break on list so I'm into it for $125. Worst case I'm out that much but have eliminated one more electronic component from the list of potential problems. If it solves I'll post one last time on full symptoms, codes and resolution actions.

 

Hey Tom, is the camaro ECM in the same waterproof housing? For some reason I thought they were diff.

 

Yes they are 93+ fbody stuff is under the hood just like the vettes.

 

Another shade-tree mechanic bites the dust!

I invested $120 (small discount, thank goodness) in the new ECM - put it in Saturday and still have the same problem. Ran fine for about 10 miles then went into "limp" mode. While trying to carefully drive it home it actually died completely while doing about 35 mph in traffic. Felt a lot like 'no spark'.Pulled into the middle of a divided street, popped the hood and smacked the ECM (getting good at doing this fast), and it started up again, so I did get it home. It loses ALL digital guages while acting up.

Tried the key on Sunday while checking electrical connections under the hood for the umpteenth time and it looked normal - like it would fire right up. Taking no more chances though. The next time I start it will be to drive (and limp) it to another mechanic - one who is more 'vette familiar. Hope the stars are in alignment.

Weather forecast for this week in Eastern WA is for 80s and clear skies all week - great top-down weather. Figures.

 

Sounds like the same thing that happened to me, except I first paid around $320 for a supposedly reman ECM and it worked for 1 day and then the car wouldn't run at all, so I put my old one back in and it fired right up. Bought a used ECM out of a running car and haven't had a problem since.

And if your not open for suggestions, don't post your problems, just put on a skirt grab a jar of vasoline and head to your local dealership.

KC

 

Shade tree - I guess I don't understand your post. I'm very open to suggestions, but the ECM replacement was MY (bad) idea - one I wasn't surprised failed. I have used the majority and appreciated all the advice I pick up on this forum.

BTW, I didn't know there was a CF member with the "Shadetree" sig - I just didn't know your are out there. I was referring to myself as the one who bit the dust.

My troubleshooting too frequently involves buying and replacing wrong parts repeatedly until I luck into a solution or pay a real mechanic to do the job correctly. That's the condition now, as a matter of fact. I was able to drive to a shop this morning, and anxiously await their notice of what they can find and fix. I'll post symptoms, efforts and results for others consideration once completed.

 

Yeah, sorry 'bout that...it had been a rough morning. But, even though the "new" ECM didnt fix it, I wouldn't rule that out just yet. Like I said, the ECM I first bought that was a reman unit worked for a day and then went out, so I would try to find one that you know for sure works and see what happens. Although, now that I think about it, when I first replaced my ECM, the car wouldn't even fire. It was after a few days of looking around for something else to be wrong (I was definitely pissed after spending $300 on that ECM just to not fix the problem, luckily I got my money back) that it decided to work, but only for a day and then nothing. Put the old one in and it fired right up with same problems as before. Now though, I've got a used ECM in it and it is still running fine.

KC

 

Not having seen a picture of an ECM / chip combination I was ignorant of how they are SUPPOSED to look. It turns out my car had a "super chip" installed piggy-back with the standard chip, and it started failing under heated conditions. I didn't know the connector / chip combination I moved from old ECM to remanufactured ECM was anything other than a stock chip. It was.

A friendly garage with 'Vette knowledge looked in the ECM, saw and removed the piggy-backed chip, and the car is now fixed. That was $108 well spent.

The "super chip" plugs into the top of a carrier which also accepts the stock chip on one side. The combination is snapped into place on the ECM.

This lack of knowledge and experience cost me a little but I'm not upset. It will be interesting to see how I think it runs now compared to before. I will be witness to whether or not this particular "super-chip" did anything noticeable for the performance.

Good luck with YOUR personal gremlins - mine has been banished.