wschmidt

Anyone know of a good place to go for ECM repair from a price/quality point of view? I have tried searching the forum, but didnt turn anything up on this....

I am almost 100% sure I have ECM issues, will know better when my OBD to PC cable shows up. I was able to take it apart, found a bad solder joint and bad trace that I repaired, but I still can't get the damn code 43 to go away and my fans seem to want to work at their leisure among other things. Kind of hard to dig in deeper without a board schematic and even then, probably just worth a couple hundred to pay someone to do it.

toptechx6

The following are all reputed to repair ECM's

acquaauto@aol.com (Louis)

http://www.siaelec.com

http://gmautocomputers.com/

http://www.bsecorp.com/

http://www.autoecms.com/

my advice however would be to purchase a Factory Service Manual to troubleshoot your code 43 which indicates a problem with the knock sensor circuit if you do not already have a copy.
If you do not have a FSM you will find that it will usually pay for itself with the first repair.
Regarding your fan running you should understand that that such operation is commanded by default when many DTC's are set by the ECM. You will probably find it will return to normal operation once you diagnose and repair the code 43.

Also see my post #2 in this thread for my own experience with code 43, good luck.

http://forums.corvetteforum.com/c4-t...old-start.html

wschmidt

I have the FSM and I followed the DTC chart. Everything checked out. I just got the car with 95k on it, so I wanted to do a coolant flush. I replaced the sensors even though they check out while I was under there and still have the code. I think I actually read that post or another similar one where someone had gone through the chart, everything checked out, and they replaced the sensors anyway and the code went away, unfortunately that isnt working for me. To date, I have done the DTC 43 chart, I have checked every ground I could find going back to the ECM for continuity (wire side of connector) to battery negative, opened the ECM to look for obvious signs of damage and repaired it. Next I am going to check the appropriate wires for continuity at the contacts on the computer side of the connector and I have an DLC to PC cable coming so I can monitor the computer.

I suspect ECM becuase I have had other symptoms. First, after prodding at all the ground wires, the code did go out for a long time, I ran the car to warm up, revved the engine up to ~2k, put the motor in gear with ebrake on under load, and the light stayed off. I shut down and check the codes, got a new code (H28), but no DTC43. I started the car again, no light, so I then started tapping and shaking the ECM and the light came on. I pulled the codes and the H43 was back. My A/C fan used to run constantly before I messed with the wires, now no fans will run at all (I let the temp get to a little over 240F), the engine fans used to cycle appropriately. Would love to know if fixing the obvious issues when I tore open the ECM has fixed anything, but I havent had a chance to mess with it enough. W/out a schematic its kind of tough to know what circuit was damaged and repaired.

Also, a couple weeks ago when I was first sorting things out, I was driving and the car shut off, it would crank and sputter occasionally, by the time I walked home and came back with tools (~1hr) the car started right up with no problem. Could be a loose connection or could be a heat issue that I have read some other people have dealt with. There was also a time where the car would just crank at cold and not start. The next day it started right up so I never really got to trouble shoot that as it is intermittant. I also have high idle, usually ~1000, sometimes up to 2000. I dont have any concrete evidence that it is ECM yet, just strong suspicion. I suppose these could all be seperate issues with the respective circuits, but ECM seems to be the only thing they have in common.

If there are any other checks I can do before throwing an ECM repair at it, I would love to hear it.

toptechx6

Good job, definitely sounds like you have done your homework. I agree that the tap and shake test would have me thinking ECM as well.
Just out of curiosity where are you located? If you happen to be nearby I can let you try my ECM before sending yours out. If not try filling out your profile and maybe another member who lives near you will do the same.
I have not used any of the companies in the links to repair a Corvette ECM, I did get one repaired by Louis (first e-mail address) for my Ram truck and it works great, hope that helps.

wschmidt

I really want to eliminate everything else before spending the money and having the down time without an ECM as there are other things I have to work through. I dont mind throwing $20 parts at a problem, but when it gets much more than that I probably spend too much time confirming.

I am in NH, I will try to update. Yes, I meant to thank you for the links, siaelec.com is half the price of the other places I have seen.

toptechx6

No need to apologize for being thorough with the diagnosis part, many skip it entirely and just start tossing parts at the problem. Hope someone close to you replies and lets you try an ECM before sending it out, but as mentioned I would feel pretty confident if the tap test turns on the MIL, again good luck.

wschmidt

So it may be a good thing that I went through this again. Somehow I overlooked a step on the DTC chart. I am only getting about 2.4V on my lines to the sensors. I think what happened is that the battery was pretty well dead from me cranking it over for a compression test and messing around with it so I just assumed at the time I would either get 4-6V or 0V and the lower voltage was because there wasn't much juice on it. Upon further examination it says that less than 4V is an open/grounded circuit or a bad ECM. If the circuit was open, I wouldn't get anything right? If it was grounded, what would I see? If I probe the wire at the ECM, I get about 1400 ohms resistance to battery terminal with both sensors plugged in and it goes up to over 2000 ohms when I unplug the drivers side sensor (cant get at the pass side without jacking up the car). Does this indicate a "grounded circuit" or am I just measuring the resistance through the sensors? I guess I really have to uplug both sensors and check for any continuity to battery terminal, kind of losing daylight for tonight.

Also, I got that ALDL cable in and was running TTS datamaster this afternoon. It kept losing the connection, it would connect and take data for about 2 seconds, lose connection, take a few seconds to re-establish the connection, and then lose it again repeatedly. Is this another sign of a bad ECM? The self test datamaster does for the connection came in good and I am pretty sure that the connections are good.

wschmidt

So upon more research, apparently you have to have both sensors unplugged to get the 4-6V. So far I have checked everything in the circuitry so I am pretty confident that it is the ECM or PROM. If I follow the DTC chart with this new information, I get to "replace PROM". How can I tell if it is an ECM issue or PROM? With the sensors unplugged and probing at the knock circuit wire at ECM, I get about 4280 ohms of resistance to batt. Is there supposed to be a resistance through the ECM or does this indicate that somehow the circuit is shorted to ground in the ECM? When I take the ECM out of the loop and still leave the sensors unplugged, I get an open circuit, so I know that there is no short in the wiring. All wiring that I can see looks good.

RACER 1993

Your ECM should be #16159278 "Right"? I sent mine in through a NAPA dealer, it was gone for about 10 days and came back. I think they charged me $190 dollars.

I have heard these ECM's are getting rare for the 1992-1993 so I decided to find a spare.
I went to Chevy dealers and the National salvage yard system and could not find one.

I did a bunch of research on this and was informed that these ECM's are getting rare, but they were not just used on Corvettes. This part number was also used on Camaros, Firebirds, Cadillacs, Impalas and Buick Roadmasters that were equipped with LT1's.

There is a difference in the PROM between a Corvette and all the others. I found a Camaro ECM on E-bay for $150 and removed the PROM and bought one at a Chevy dealer.
The Camaro PROM did have a different part number.
I now have a complete spare unit and I have had it in the car and scanned with Datamaster and seen no difference.

When I searched E-Bay for an ECM, there are hundreds of them listed. I could not find one using the search for a "Corvette ECM", so I searched for a "Chevrolet ECM". I found hundreds of pictures to look at until I found one. I also found one just listed under "ECM".

I have only had a knock sensor alarm one time. The car had been sitting quite a while and the battery was low on charge and it was a little jerky on the start. I charged the battery, cleared the alarm and it seems to be OK now.

RACER 1993

The knock sensors are down low where they can get into weather. You might want to take some electronic spray cleaner and clean the connectors.

Sometimes it seems that a little low voltage from a dirty or loose connection can cause a lot of grief.

My wife's car used to set alarms because the negative battery terminal used to corrode.
After cleaning the stupid terninal a few times I just bought a new one. Her car is only a couple of years old.

RACER 1993

There is a used ECM on E-bay, listed by a guy calling himself Army_Guy. Its item #140738387101. For $350. You can see that they gave the harness a haircut. It says it came from a Trans-AM, but you can read the label and see if its your right part number. It should be, although the PROM module will not work for you and will have to be replaced. You can use the PROM from your ECM.

1992 and 1993 Corvettes with LT1's used this. I don't know what year the other cars used them.

Sadly they make a point of changing the connectors and the wiring to make these things less interchangeable.

Designed obsolescence. The price just keeps going up for this part number.

wschmidt

I see that listing. I think I found a used corvette ECM with PROM for ~$300. I may just pick that up, as the PROMs seem hard to find too and he has some other parts I want so it will be one stop shopping. I know it isnt the sensors or the circuit, at this point I have been through everything and I am pretty sure it is the ECM. I have some other issues that are most likely ECM related too. I do have the 16159278 part number. Thanks for the tip on other models that use it, I will do a search and see if I can't find something cheaper.

RACER 1993

I figured it was a good idea to have a spare, when I ever sell the car, I'm sure the next owner will like having a spare too.

toptechx6

In case you haven't done so already before ordering an ECM or PROM, I would make sure the existing PROM is properly seated as that could cause identical symptoms, hope it is something that simple.

wschmidt

I have already pulled the whole ECM apart and used contact cleaner and re-seated the PROM. Same issues. Knowing a little more and following the DTC 43 chart, I get to replace PROM. I think it is worth the money to invest in spares so I am just going to suck it up. I have basically chased this down as much as I can, time to buy some parts...

JM95

Try www.ecsmodules.com or call at 888-593-2261

wschmidt

Found a whole new ECM with PROM from Shawn at Corvette Nutz for a good deal. Now I will have a spare and not have to worry about down time if one is getting replaced.

jaa1992

Shawn is good people!

wschmidt

Put in the new ECM and the light is out! Now I just need to find someone around NH to tune it for me....

HlhnEast

Good you got it solved. I was going to suggest that if you do send out your old unit to ask if the repair shop will need the PROM installed or if for sure they will ship it back to you. If your buying a rebuilt ECM ask if the PROM is included so you know whether or not to keep yours. As mentioned the ECMs fit several models but the PROM is specific and VERY hard to replace