81 Corvette Solid Check Engine light!
Thread Starter
Cruising
Joined: Dec 2011
Posts: 10
Likes: 0
81 Corvette Solid Check Engine light!
I have 81 vette and I have check engine light on. I tried to retrieve the code but for some reason the light would not blink and I even tried disconnecting my battery to see if it will go away...no luck! What do you guys think is wrong and how can I make it blink to get the code? Thank you in advance for all feed back.
Melting Slicks
Joined: Mar 2006
Posts: 2,465
Likes: 0
From: Orange Park Fl
I have an old OTC Monitor 2000 that reads the codes, but there is a way to short two of the terminals on the connector and make it blink the codes. I don't remember off hand exactly how to do this. If you tried this and it did not work, I would double check that you have the right proceedure. If you need me to, I'll look it up for you.
God bless, Sensei
God bless, Sensei
Instructor
Joined: Apr 2011
Posts: 137
Likes: 0
From: Goose Creek SC
i have an 81 also. Does your car still have the computer (ECM). I'm new to the site, however, it sounds like you may not have the ECM connected. How is the car running, rich? I take it that you know where the ALDL connector is located, it is under the ashtray. Code 12 (one long and two short blinks) is the standard everthing is okay code. All you need is a flat head screw driver. I will help if you need some more info.
Mark (still a learning rookie)
Mark (still a learning rookie)
Racer
Joined: Nov 2011
Posts: 319
Likes: 12
From: South Chase WI
First look behind the driver seat, in the battery area, and the ecm is right in front of the battery.
The connector under the ashtray, 5 terminals, from left to right A thru E....the 2 right most terminals, D and E are for diagnostic; the last one, E, being chassis ground. Touch these 2 together, D and E, with the key on, no engine running. Wait, it takes a few seconds, listen for clicking, light should begin to flash. If it stays on, use a wire to known chassis ground and touch it to the second terminal in from the right, D. See if it goes into diagnostic. If yes E is no longer grounded. Just use the test wire ground, or look for why E is no longer grounded, broken, corroded, etc.
If not, pull ecm out of bracket, leave plugged in, look closely at the plugs, they are labeled... and ground terminal "5" on the ecm plug (still plugged in). Also check for 12v+ on terminal "R" on the ecm, this is the power to it, should be continuous. Should go into diagnostic, code "12" 3 times, then your trouble code(s) after that. Let us know what you get.
Hope this helps.
The connector under the ashtray, 5 terminals, from left to right A thru E....the 2 right most terminals, D and E are for diagnostic; the last one, E, being chassis ground. Touch these 2 together, D and E, with the key on, no engine running. Wait, it takes a few seconds, listen for clicking, light should begin to flash. If it stays on, use a wire to known chassis ground and touch it to the second terminal in from the right, D. See if it goes into diagnostic. If yes E is no longer grounded. Just use the test wire ground, or look for why E is no longer grounded, broken, corroded, etc.
If not, pull ecm out of bracket, leave plugged in, look closely at the plugs, they are labeled... and ground terminal "5" on the ecm plug (still plugged in). Also check for 12v+ on terminal "R" on the ecm, this is the power to it, should be continuous. Should go into diagnostic, code "12" 3 times, then your trouble code(s) after that. Let us know what you get.
Hope this helps.
Thread Starter
Cruising
Joined: Dec 2011
Posts: 10
Likes: 0
I have an old OTC Monitor 2000 that reads the codes, but there is a way to short two of the terminals on the connector and make it blink the codes. I don't remember off hand exactly how to do this. If you tried this and it did not work, I would double check that you have the right proceedure. If you need me to, I'll look it up for you.
God bless, Sensei
God bless, Sensei
Thread Starter
Cruising
Joined: Dec 2011
Posts: 10
Likes: 0
i have an 81 also. Does your car still have the computer (ECM). I'm new to the site, however, it sounds like you may not have the ECM connected. How is the car running, rich? I take it that you know where the ALDL connector is located, it is under the ashtray. Code 12 (one long and two short blinks) is the standard everthing is okay code. All you need is a flat head screw driver. I will help if you need some more info.
Mark (still a learning rookie)
Mark (still a learning rookie)
I know where the connector to get the code and I grounded the terminal to get the light to blink but no luck.
Thread Starter
Cruising
Joined: Dec 2011
Posts: 10
Likes: 0
First look behind the driver seat, in the battery area, and the ecm is right in front of the battery.
The connector under the ashtray, 5 terminals, from left to right A thru E....the 2 right most terminals, D and E are for diagnostic; the last one, E, being chassis ground. Touch these 2 together, D and E, with the key on, no engine running. Wait, it takes a few seconds, listen for clicking, light should begin to flash. If it stays on, use a wire to known chassis ground and touch it to the second terminal in from the right, D. See if it goes into diagnostic. If yes E is no longer grounded. Just use the test wire ground, or look for why E is no longer grounded, broken, corroded, etc.
If not, pull ecm out of bracket, leave plugged in, look closely at the plugs, they are labeled... and ground terminal "5" on the ecm plug (still plugged in). Also check for 12v+ on terminal "R" on the ecm, this is the power to it, should be continuous. Should go into diagnostic, code "12" 3 times, then your trouble code(s) after that. Let us know what you get.
Hope this helps.
The connector under the ashtray, 5 terminals, from left to right A thru E....the 2 right most terminals, D and E are for diagnostic; the last one, E, being chassis ground. Touch these 2 together, D and E, with the key on, no engine running. Wait, it takes a few seconds, listen for clicking, light should begin to flash. If it stays on, use a wire to known chassis ground and touch it to the second terminal in from the right, D. See if it goes into diagnostic. If yes E is no longer grounded. Just use the test wire ground, or look for why E is no longer grounded, broken, corroded, etc.
If not, pull ecm out of bracket, leave plugged in, look closely at the plugs, they are labeled... and ground terminal "5" on the ecm plug (still plugged in). Also check for 12v+ on terminal "R" on the ecm, this is the power to it, should be continuous. Should go into diagnostic, code "12" 3 times, then your trouble code(s) after that. Let us know what you get.
Hope this helps.
I'll try this one when I get home.
thanks and I will let you guys know.
Instructor
Joined: Jun 2008
Posts: 164
Likes: 0
From: Groton MA
If you disconnected the ECM and the light is still on then it sounds like you have a short to ground somewhere between the light and the ECM. The light has 12V applied to it all the time and the light is lit by the ECM completing the path to ground. Check the wire from the ECM to the light for continuity to ground. If memory serves me correctly it is G on the ECM connector or B (2nd form the left) on the connector under the ashtray.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Thread Starter
Cruising
Joined: Dec 2011
Posts: 10
Likes: 0
If you disconnected the ECM and the light is still on then it sounds like you have a short to ground somewhere between the light and the ECM. The light has 12V applied to it all the time and the light is lit by the ECM completing the path to ground. Check the wire from the ECM to the light for continuity to ground. If memory serves me correctly it is G on the ECM connector or B (2nd form the left) on the connector under the ashtray.
How much usually a ECM go for this car?
Racer
Joined: Nov 2011
Posts: 319
Likes: 12
From: South Chase WI
Not much. Get a new one, not used, and pull the PROM out of the old one to put in the new one. Just did mine, $100.
Maintenance free sealed battery is a must, the ones with caps that gas when charged / not maintained will corrode the ecm.
Maintenance free sealed battery is a must, the ones with caps that gas when charged / not maintained will corrode the ecm.
Instructor
Joined: Oct 2010
Posts: 113
Likes: 5
From: Dwingeloo Netherlands
Had the same; light would stay on and would never blink, whatever I did.
Had the ECM tested in another car, and in that car also the light would not blink, but stayed on.
A new ECM resolved the problem.
Cor
Had the ECM tested in another car, and in that car also the light would not blink, but stayed on.
A new ECM resolved the problem.
Cor
Thread Starter
Cruising
Joined: Dec 2011
Posts: 10
Likes: 0
I finally replaced the ECM back in early January this year and its been good since till the other day. The check engine light came on and I pulled the code and it was code 51 which is bad PROM. Also my car is misfiring when its running on gear and hesitating, but when i put on neutral and floor it, it runs ok...no misfire.
So guys think the prom is causing it? Where can i get a new prom replacement?
So guys think the prom is causing it? Where can i get a new prom replacement?
Burning Brakes
Joined: Oct 2011
Posts: 956
Likes: 86
From: McDonough Georgia
Zip Corvette seems to have the parts for about 300 to replace the ccu and the prom.
http://www.zip-corvette.com/GroupDet...2+Rebuilt+ECM&
Then again, the whole mess could be thrown out and the Rochester retuned for an increase in performance and much cheaper.
http://www.zip-corvette.com/GroupDet...2+Rebuilt+ECM&
Then again, the whole mess could be thrown out and the Rochester retuned for an increase in performance and much cheaper.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Now that you have changed the ECM, have you [again] tried to retrieve the trouble codes stored in the [new] ECM? You should do that.
And, if you still can't retrieve them, your PROM is likely defective.
And, if you still can't retrieve them, your PROM is likely defective.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Know this is an older thread revived, but since you're talking 81', assume the car has an electronically controlled carburator. These carbs have M/C(mixture control) soleniods, that tend to go bad over time. There's rubber tipped metering rods in these that can harden and break off. Car will run ruff, and though a code. Alcohol infused gas certainly isn't helping things here.