Topic: Check engine light will not go off or flash
in Forum: C3 Electrical
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Fuse has power,
I tried the paper clip Light does not flash,
Checked grounds all good,
Cleaned the edge connectors cleaned up
New battery
Replaced alternator
I am thinking a defective ECM
I did see some corrosion on the bolts the bolt the ECM together the car sat for some time
|UPDATED|11/25/2013 8:13:08 PM (AZT)|/UPDATED|
|UPDATED|11/25/2013 8:13:08 PM (AZT)|/UPDATED|
1981 Vette
auto
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Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The fuse that operates the "Check Eng" light powers a lot of stuff(Gauges fuse).
The ground for the light comes directly from the ECM. You may have a short to ground in the brown/white wire going to the light, or the ECM may be bad, as you suspect. If it were me, I would remove the ECM, and take the cover(s) off, and have a look-see inside first.
It's possible the oxygen sensor(s) are open/shorted out, too. The check engine light is really to tell you if the ECM has gone into "closed loop" or not. It will not go into closed loop until it sees a valid, switching signal from the O2 sensors. So...you could have one of several issues that would cause the problem.
Does the car run ok?
Joel Adams
C3VR Lifetime Member #56 
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The light staying on is either a "hard" code, or a short in the wiring for the light itself. If jumping the ALDL terminals does not cause the light to flash codes, you must have a short, or a problem with the ECM. 
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Former Member
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Oak Creek, WI - USA
Joined: 5/21/2008
Posts: 1965
Vette(s): 1981 Great White Shark. Red Interior, 350/190 hp. PS, PB (SS), A/C CC, T-Tops. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vettes Car Club. 175,000 Original miles!! Now own a 1998 C-5!
I had that problem awhile back with my 81. I replaced the PROM and everything worked just fine!!!
Dan da Man (^^^)
Former Member
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Oak Creek, WI - USA
Joined: 5/21/2008
Posts: 1965
Vette(s): 1981 Great White Shark. Red Interior, 350/190 hp. PS, PB (SS), A/C CC, T-Tops. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vettes Car Club. 175,000 Original miles!! Now own a 1998 C-5!
stutrac said: Where do I get the prom? Cost?
In will check out the prices and then let you know. If push comes to shove, I have and ECM and PROM that I keep as an "extra" for my car!!
Dan
i borrowed a ECM from a local person and i still have the check engine light on, the clicking has gone and sounds really good so i solved 1 issue now if i could get the light off or i may just pull the bulb and be done
1981 Vette
auto
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Have you tried to pull any codes with the other ECM?
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
as mentioned above have you disconnected the ECM to see if the light stays on with ECM disconnected. Which would indicate that the brn/wht wire would be grounded somewhere.
Zip has parts
Which pins are you jumping for ECM diagnostics A-grnd B- Diagnostic.
in Forum: C3 Electrical
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