Looking for ECM Information
Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
Looking for ECM Information
Some may remember the post I made about my 95 that had cut out will I was driving. I had it towed to garage I use since they would have diagnostic tools I don't have. It was originally thought that the fuel pump was the problem because at that time was showing no fuel pressure but while playing with it was found that the pump did rum of the few second prime but still would only crank. The attention then went to the ECM because the old OBD1 they hooked up indicated the ECM is not sending the required signals..
Keeping in mind no codes are showing can someone provide me with the best way to confirm the issue is indeed with the ECM? If additional diagnostics proves it is the ECM what venders are recommended to rebuild it at a reasonable cost and time frame??
Keeping in mind no codes are showing can someone provide me with the best way to confirm the issue is indeed with the ECM? If additional diagnostics proves it is the ECM what venders are recommended to rebuild it at a reasonable cost and time frame??
Burning Brakes
Joined: Aug 2008
Posts: 913
Likes: 229
From: Tampa, FL
Some may remember the post I made about my 95 that had cut out will I was driving. I had it towed to garage I use since they would have diagnostic tools I don't have. It was originally thought that the fuel pump was the problem because at that time was showing no fuel pressure but while playing with it was found that the pump did rum of the few second prime but still would only crank. The attention then went to the ECM because the old OBD1 they hooked up indicated the ECM is not sending the required signals..
Keeping in mind no codes are showing can someone provide me with the best way to confirm the issue is indeed with the ECM? If additional diagnostics proves it is the ECM what venders are recommended to rebuild it at a reasonable cost and time frame??
Keeping in mind no codes are showing can someone provide me with the best way to confirm the issue is indeed with the ECM? If additional diagnostics proves it is the ECM what venders are recommended to rebuild it at a reasonable cost and time frame??
The ECM itself, if you can ground out the diagnostic wire, will flash the "SERVICE ENGINE SOON" light, and this is the old school way of getting ECM codes, to see if your ECM is actually good. You should get a CODE 12, which will look like this, "FLASH - PAUSE - FLASH FLASH" and then it will do it two more times. After that, you should see some other flashes if there are actual trouble codes... and it'll flash each trouble code three times, and then finally, it'll go back to flashing code 12. If you just get a steady flash that doesn't end... or no flash at all, that usually means there's something actually wrong with the ECM itself.
Here is a video that explains how to check the codes "the old way" in a newer C4 Corvette (not my video):
If you get a code 12 (as indicated), then your ECM is actually OK, and then it's probably something else.
Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
They had an older OBD1 tester at the garage which showed no codes while showing information that indicated the ECM wasn't sending certain signals. It is very easy to show codes on a 95 by shorting the 4 and 12 pin of the OBD connector. Some members here are very knowledgeable in diagnostics of the ECM so hoping they can direct me in that regard.
Burning Brakes
Joined: Aug 2008
Posts: 913
Likes: 229
From: Tampa, FL
They had an older OBD1 tester at the garage which showed no codes while showing information that indicated the ECM wasn't sending certain signals. It is very easy to show codes on a 95 by shorting the 4 and 12 pin of the OBD connector. Some members here are very knowledgeable in diagnostics of the ECM so hoping they can direct me in that regard.
Burning Brakes
Joined: Aug 2008
Posts: 913
Likes: 229
From: Tampa, FL
You asked this: "can someone provide me with the best way to confirm the issue is indeed with the ECM?"
This is it. If you're not getting a flashing service engine soon, then yes, your ECM is dead, or the pins on the ECM harness connector are unsoldering from the board and you need to send it in for repair or repair it yourself with a soldering iron.
I'm trying not to be mean here... but I get so frustrated on Corvette Forum sometimes because like HALF the posts are people who refuse to do even the most basic work on their car, but waste everyone's time and then take it to a shop anyway, get screwed, and the car ends up on eBay or Bring a Trailer.
Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
Dude... is this work beneath you? Stick the pin in and try it yourself. I don't trust mechanics, certainly not the younger ones who have no idea what OBD1 even is.
You asked this: "can someone provide me with the best way to confirm the issue is indeed with the ECM?"
This is it. If you're not getting a flashing service engine soon, then yes, your ECM is dead, or the pins on the ECM harness connector are unsoldering from the board and you need to send it in for repair or repair it yourself with a soldering iron.
I'm trying not to be mean here... but I get so frustrated on Corvette Forum sometimes because like HALF the posts are people who refuse to do even the most basic work on their car, but waste everyone's time and then take it to a shop anyway, get screwed, and the car ends up on eBay or Bring a Trailer.
You asked this: "can someone provide me with the best way to confirm the issue is indeed with the ECM?"
This is it. If you're not getting a flashing service engine soon, then yes, your ECM is dead, or the pins on the ECM harness connector are unsoldering from the board and you need to send it in for repair or repair it yourself with a soldering iron.
I'm trying not to be mean here... but I get so frustrated on Corvette Forum sometimes because like HALF the posts are people who refuse to do even the most basic work on their car, but waste everyone's time and then take it to a shop anyway, get screwed, and the car ends up on eBay or Bring a Trailer.
One more bit of information I can add to all of this is I do remember the tachometer never moved while the engine was cranking. I do remember reading threads in this Forum that it be important diagnosis information for some issues.
Last edited by CorvetteRules; May 27, 2026 at 07:15 PM. Reason: Spelling
Burning Brakes
Joined: Aug 2008
Posts: 913
Likes: 229
From: Tampa, FL
Why are you so butt hurt? The SES light did not come on so I'm not surprised about no code. In the car just died while I was going down the road. It just cranked with no indication of ignition. I had AAA take it to garage I've used for my vehicle for over 30 years with 2 older mechanics that originally worked in Chevy dealers. They would have more experience then I could ever have with a thirty year old car. I have completed a number of repairs on my 95 since owning like different sensors and fuel pump. Your reaction troubles me. I know very little on diagnostic steps on the ECM which is why I came here to get help. With the information I get here I can intelligently talk with the mechanics at the garage. If you think what I'm asking is a waste of your time you have the right for that opinion but I'm hoping I can get some ECM diagnostic information that will help me ensure I'm going in the right direction. While I've known the mechanics for many, many years I still want to be able to ask them questions
One more bit of information I can add to all of this is I do remember the tachometer never moved while the engine was cranking. I do remember reading threads in this Forum that it be important diagnosis information for some issues.
One more bit of information I can add to all of this is I do remember the tachometer never moved while the engine was cranking. I do remember reading threads in this Forum that it be important diagnosis information for some issues.
1 - Did you, or did you not put a paper clip in the ALDL connector and see if it gives you code 12?
2 - If you saw nothing, you can also try checking to make sure that you don't have a blown ECM fuse (I think it's slot 33 in the fuse panel)
3 - If the fuse is fine, and you don't get a flashing SES code, then it's possibly a bad connection at the ECM (try jiggling it), or the ECM itself is bad.
For these older ECMs for your year of Corvette, it is a known issue for the pins to desolder from the board, and break connection. There is a shop that a lot of people here use to have their ECM's repaired.
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Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
The vehicle is not at my house and my schedule has not allowed me to go to location it is at, but I have no issue with confirming some basics when I can see it in person. I actually have a male OBDll connector that I shorted out the 4 and 12 pins so I don't have to crawl under the dash to use a paperclip since the OBD scanner I have that reads l and ll gets an error message reading my 95.
The information you just provided is the type of information I was hoping for to feel good before I send the ECM out for repair. Some of the ECM repair sites I have checked into have wide variations in cost and timetable for return. I will check the items you mentioned when I can go to where the car is. Your help is greatly appreciated. To me this is why this Forum is such an important place for owners seeking an education.
The information you just provided is the type of information I was hoping for to feel good before I send the ECM out for repair. Some of the ECM repair sites I have checked into have wide variations in cost and timetable for return. I will check the items you mentioned when I can go to where the car is. Your help is greatly appreciated. To me this is why this Forum is such an important place for owners seeking an education.
Burning Brakes
Joined: Aug 2008
Posts: 913
Likes: 229
From: Tampa, FL
The vehicle is not at my house and my schedule has not allowed me to go to location it is at, but I have no issue with confirming some basics when I can see it in person. I actually have a male OBDll connector that I shorted out the 4 and 12 pins so I don't have to crawl under the dash to use a paperclip since the OBD scanner I have that reads l and ll gets an error message reading my 95.
The information you just provided is the type of information I was hoping for to feel good before I send the ECM out for repair. Some of the ECM repair sites I have checked into have wide variations in cost and timetable for return. I will check the items you mentioned when I can go to where the car is. Your help is greatly appreciated. To me this is why this Forum is such an important place for owners seeking an education.
The information you just provided is the type of information I was hoping for to feel good before I send the ECM out for repair. Some of the ECM repair sites I have checked into have wide variations in cost and timetable for return. I will check the items you mentioned when I can go to where the car is. Your help is greatly appreciated. To me this is why this Forum is such an important place for owners seeking an education.
@IHBD knows the name of the specific shop. If the connectors are screwed up, he can recommend the right place to send your ECM.
Team Owner
Joined: Sep 2003
Posts: 25,413
Likes: 2,745
I believe it would be good to first understand that your '95 does NOT have a traditional ECM. '95 was the second year for the PCM in the corvette. There should be many, some maybe even somewhat local that understand 'The PCM'. You need to understand the diagnostics involved and start from scratch. NJ location there actually might be tuners that could evaluate your car while running and do some diagnostics for you. I don't believe you just ship and pray that it will return fixed.
Start diagnostics from scratch!
Start diagnostics from scratch!
Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
I believe it would be good to first understand that your '95 does NOT have a traditional ECM. '95 was the second year for the PCM in the corvette. There should be many, some maybe even somewhat local that understand 'The PCM'. You need to understand the diagnostics involved and start from scratch. NJ location there actually might be tuners that could evaluate your car while running and do some diagnostics for you. I don't believe you just ship and pray that it will return fixed.
Start diagnostics from scratch!
Start diagnostics from scratch!
Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
I was able to look at my 95 for a few minutes today and shorted 4 and 12 pin and came up with H codes 31,33,35,37,72 and 74. It appears the 30 codes all concern the CCM and I don't know if any of those have any relationship to an ECM/PCM issue. I didn't clear the codes since the car is not running so I couldn't see if codes reappeared. Unfortunately I forgot to check the ECM fuse so will have to look next time I can get over there.
With the key to the run position the SES light stayed on steady with no blinking. I can hear the fuel pump run to prime but no fuel pressure and car just cranks. Does the information above give anyone additional diagnostic steps I should attempt??
With the key to the run position the SES light stayed on steady with no blinking. I can hear the fuel pump run to prime but no fuel pressure and car just cranks. Does the information above give anyone additional diagnostic steps I should attempt??
Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
From the research I've done a code 33 would make the 95 run rough but wouldn't keep it from firing. Since I have limited knowledge on it I won't feel bad if someone tells me my research is flawed.
Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
I can confirm that there is power to the ECM/PCM so that's not a problem. My mechanic does have a flow chart for the 95 ECM/PCM to help diagnose issues with signals to appropriate systems. I have a digital FSM but I'm having trouble finding the appropriate pages for diagnostic steps, but will keep searching.
Also searched for vendors that rebuild the existing ECM/PCM to original using the vehicle vin and milage. Not cheap and would have to mail to them.
As WVZR-1 suggested I looked for any "Tuners" that may be able to provide assistant but only found one in north Jersey and while their website shows they do Corvettes it appears only C-5's and newer.
Getting frustrated going from a car that was running perfectly to now a doorstop. But a Corvette fan never gives up so forward I go.
Also searched for vendors that rebuild the existing ECM/PCM to original using the vehicle vin and milage. Not cheap and would have to mail to them.
As WVZR-1 suggested I looked for any "Tuners" that may be able to provide assistant but only found one in north Jersey and while their website shows they do Corvettes it appears only C-5's and newer.
Getting frustrated going from a car that was running perfectly to now a doorstop. But a Corvette fan never gives up so forward I go.
Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
UPDATE
The mechanic where my 95 is at tried a different "old" scanner to pull codes and that scanner showed a 16 code. With it showing that code now confuses me because when I shorted the 4 and 12 pin it didn't show a 16. Question I now have is has any of you had their opti go bad and not have a 16 code using the "paper clip" method of pulling codes??
I'm the second owner and have no information regarding the opti because I bought it from a dealer that bought it at auction when the original owner traded it in at a BMW dealer.
The mechanic where my 95 is at tried a different "old" scanner to pull codes and that scanner showed a 16 code. With it showing that code now confuses me because when I shorted the 4 and 12 pin it didn't show a 16. Question I now have is has any of you had their opti go bad and not have a 16 code using the "paper clip" method of pulling codes??
I'm the second owner and have no information regarding the opti because I bought it from a dealer that bought it at auction when the original owner traded it in at a BMW dealer.
Burning Brakes
Joined: Aug 2008
Posts: 913
Likes: 229
From: Tampa, FL
UPDATE
The mechanic where my 95 is at tried a different "old" scanner to pull codes and that scanner showed a 16 code. With it showing that code now confuses me because when I shorted the 4 and 12 pin it didn't show a 16. Question I now have is has any of you had their opti go bad and not have a 16 code using the "paper clip" method of pulling codes??
I'm the second owner and have no information regarding the opti because I bought it from a dealer that bought it at auction when the original owner traded it in at a BMW dealer.
The mechanic where my 95 is at tried a different "old" scanner to pull codes and that scanner showed a 16 code. With it showing that code now confuses me because when I shorted the 4 and 12 pin it didn't show a 16. Question I now have is has any of you had their opti go bad and not have a 16 code using the "paper clip" method of pulling codes??
I'm the second owner and have no information regarding the opti because I bought it from a dealer that bought it at auction when the original owner traded it in at a BMW dealer.
I'm also skeptical of every single mechanic, which is why I do everything myself. I'd almost wonder if you didn't see this code pulled directly, if perhaps he just said this and is assuming it's the OptiSpark.
Thread Starter
Drifting
Joined: Nov 2018
Posts: 1,811
Likes: 580
From: Mays Landing, NJ
I also believe in the measure twice cut once philosophy so plan on visiting them and finding out what device was actually used to pull that code and have them use it to show me. Although the fact that it just cranks and has fuel pressure does point to an ignition problem.
Last edited by CorvetteRules; Jun 4, 2026 at 01:14 PM. Reason: Spelling
Burning Brakes
Joined: Aug 2008
Posts: 913
Likes: 229
From: Tampa, FL
I also believe in the measure twice cut once philosophy so plan on visiting them and finding out what device was actually used to pull that code and have them use it to show me. Although the fact that it just cranks and has fuel pressure does point to an ignition problem.
