1981 Check Engine Light not working
Thread Starter
Intermediate
Joined: Dec 2003
Posts: 26
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From: Live Music Capital of the World
1981 Check Engine Light not working
After buying a 1981, I immediately de-smogged it and added headers, thinking I would tune it afterwards.
Then I learned about the electric carb and ECM. Well, before gutting it all out, I would like to see if the new exhaust will work with the original carb.
Now, I want to diagnose any possible ECM codes by following the Service Manual diagnostic flow chart, but first my Check Engine Light needs to be working. With ignition turned "ON" and engine stopped, the "CHECK ENGINE" LAMP should be "ON".
This is a bulb check to indicated that the lamp is working.
Unfortunately, my CE light does not come on at all. Other indicators do, like battery and seatbelt. So, I checked that all fuses are ok. Which fuse is it anyway? The manual and fusebox labels are not clear.
Then I pulled the CE bulb, it tested ok, so I reinstalled.
Next, I completely disconnected the ECM. Again, the CE Light does not come on at all. With the ECM disconnected shouldn't it come on? Ground connections seem good, but I will check again before possibly purchasing a new ECM.
Any help is appreciated.
Then I learned about the electric carb and ECM. Well, before gutting it all out, I would like to see if the new exhaust will work with the original carb.
Now, I want to diagnose any possible ECM codes by following the Service Manual diagnostic flow chart, but first my Check Engine Light needs to be working. With ignition turned "ON" and engine stopped, the "CHECK ENGINE" LAMP should be "ON".
This is a bulb check to indicated that the lamp is working.
Unfortunately, my CE light does not come on at all. Other indicators do, like battery and seatbelt. So, I checked that all fuses are ok. Which fuse is it anyway? The manual and fusebox labels are not clear.
Then I pulled the CE bulb, it tested ok, so I reinstalled.
Next, I completely disconnected the ECM. Again, the CE Light does not come on at all. With the ECM disconnected shouldn't it come on? Ground connections seem good, but I will check again before possibly purchasing a new ECM.
Any help is appreciated.
Race Director
Joined: Mar 2017
Posts: 11,953
Likes: 4,510
From: Virginia
Does your budget allow for replacing the carb and distributor? My 80 is similarly configured, except for your ECM-specific parts.
Perhaps read through this thread. If it were my car, I'd yank it all out, and install a GM distributor, and whatever carb you are comfortable tuning, or jump to a Holley Sniper EFI system.
https://www.corvetteforum.com/forums...ld-you-do.html
But it's your money, not mine.
Perhaps read through this thread. If it were my car, I'd yank it all out, and install a GM distributor, and whatever carb you are comfortable tuning, or jump to a Holley Sniper EFI system.
https://www.corvetteforum.com/forums...ld-you-do.html
But it's your money, not mine.
Disabled by request 8 JUN 2025
Joined: May 2019
Posts: 329
Likes: 94
From: St. Augustine, FL
Ecm
I'm not trying to steal this thread, but it is related...…. If the carb and distributor on an '81 have been replaced with earlier models, should the ECM be disconnected?
Race Director
Joined: Oct 2019
Posts: 10,735
Likes: 63
From: Deep in the Pisgah National Forest
After buying a 1981, I immediately de-smogged it and added headers, thinking I would tune it afterwards.
Then I learned about the electric carb and ECM. Well, before gutting it all out, I would like to see if the new exhaust will work with the original carb.
Now, I want to diagnose any possible ECM codes by following the Service Manual diagnostic flow chart, but first my Check Engine Light needs to be working. With ignition turned "ON" and engine stopped, the "CHECK ENGINE" LAMP should be "ON".
This is a bulb check to indicated that the lamp is working.
Unfortunately, my CE light does not come on at all. Other indicators do, like battery and seatbelt. So, I checked that all fuses are ok. Which fuse is it anyway? The manual and fusebox labels are not clear.
Then I pulled the CE bulb, it tested ok, so I reinstalled.
Next, I completely disconnected the ECM. Again, the CE Light does not come on at all. With the ECM disconnected shouldn't it come on? Ground connections seem good, but I will check again before possibly purchasing a new ECM.
Any help is appreciated.
Then I learned about the electric carb and ECM. Well, before gutting it all out, I would like to see if the new exhaust will work with the original carb.
Now, I want to diagnose any possible ECM codes by following the Service Manual diagnostic flow chart, but first my Check Engine Light needs to be working. With ignition turned "ON" and engine stopped, the "CHECK ENGINE" LAMP should be "ON".
This is a bulb check to indicated that the lamp is working.
Unfortunately, my CE light does not come on at all. Other indicators do, like battery and seatbelt. So, I checked that all fuses are ok. Which fuse is it anyway? The manual and fusebox labels are not clear.
Then I pulled the CE bulb, it tested ok, so I reinstalled.
Next, I completely disconnected the ECM. Again, the CE Light does not come on at all. With the ECM disconnected shouldn't it come on? Ground connections seem good, but I will check again before possibly purchasing a new ECM.
Any help is appreciated.
Clean all your connectors using electrical contact cleaner and an old toothbrush. Then hit them with a shot of silicone spray lube to reassemble. Both are available at Home improvement stores, electrical isle.
My ECU was toast. A rebuild was $82 over the counter at Autozone.
