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Topic: Check engine light will not go off or flash

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Check engine light will not go off or flash (1/25)
11/25/13 11:13pm

stutrac
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Bethany, CT - USA

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1981

Joined: 11/14/2013
Posts: 32

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|

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Re: Check engine light will not go off or flash (2/25)
11/25/13 11:53pm

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Duncanville, TX - USA

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#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

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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?

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Re: Check engine light will not go off or flash (3/25)
11/26/13 7:15am

stutrac
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Bethany, CT - USA

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1981

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car runs good,i even tried to disconnect the Negitive battery terminal to clear code's and that did not work light still on.

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Re: Check engine light will not go off or flash (4/25)
11/26/13 8:20am

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Duncanville, TX - USA

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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. Ouch

Ouch

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Re: Check engine light will not go off or flash (5/25)
11/26/13 1:22pm

dskopp
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Oak Creek, WI - USA

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1981 Great White Shark. Red Interior, 350/190hp. PS, PB (SS), A/C CC, T-Tops, Going to remain as Stock as possible. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vetts Car Club. 175,000 Original miles!!

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I had that problem awhile back with my 81. I replaced the PROM and everything worked just fine!!!

Dan da Man (^^^)

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Re: Check engine light will not go off or flash (6/25)
11/26/13 3:38pm

stutrac
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Bethany, CT - USA

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Where do I get the prom? Cost?

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Re: Check engine light will not go off or flash (7/25)
11/29/13 1:37pm

dskopp
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Oak Creek, WI - USA

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1981 Great White Shark. Red Interior, 350/190hp. PS, PB (SS), A/C CC, T-Tops, Going to remain as Stock as possible. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vetts Car Club. 175,000 Original miles!!

Joined: 5/21/2008
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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

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Re: Check engine light will not go off or flash (8/25)
12/2/13 10:27pm

stutrac
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Bethany, CT - USA

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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

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Re: Check engine light will not go off or flash (9/25)
12/3/13 1:21pm

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Duncanville, TX - USA

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Have you tried to pull any codes with the other ECM?

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Re: Check engine light will not go off or flash (10/25)
12/3/13 1:27pm

rraider1
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Woodland, WA - USA

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1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion

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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

http://www.zip-corvette.com/GroupDetails/SubGroupResults.aspx?gid=%7B6e5673b1-64ed-4ad9-a275-98e787e67fff%7D&SearchType=_GROUP_SEARCH&GroupName=80-82+Rebuilt+ECM

Which pins are you jumping for ECM diagnostics A-grnd B- Diagnostic.

Re: Check engine light will not go off or flash (11/25)
12/3/13 8:30pm

stutrac
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Bethany, CT - USA

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yes i tried to pull codes and no light flashing i used the last 2 pins on the right side

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Re: Check engine light will not go off or flash (12/25)
12/3/13 11:35pm

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Duncanville, TX - USA

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If jumpering the A & B pins does NOT cause the light to flash codes, or at least a code 12(meaning no codes stored) with two different ECMs, there has to be a problem in the circuit for the light itself. Ouch

Ouch

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Re: Check engine light will not go off or flash (13/25)
12/4/13 12:20am

rraider1
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Woodland, WA - USA

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To clarify the question

With the ECM completely disconnected Does the check engine light remain On?

If the answer is yes the problem would be an issue in the BRN/WHT wire from the ECM to the check engine light assembly

If no and you believe the ECM to be good. you would need to look at the wiring to ECM

Re: Check engine light will not go off or flash (14/25)
12/4/13 11:30pm

stutrac
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Bethany, CT - USA

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1981

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Posts: 32

mine is a 5

(modified large image to link-aapple)

|UPDATED|12/4/2013 8:30:14 PM (AZT)|/UPDATED|

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Re: Check engine light will not go off or flash (15/25)
12/5/13 8:20am

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Duncanville, TX - USA

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Dangit....that's right.
In that case, you need this diagram....

When you jump the A & B terminals, and turn the key on, you should be able to hear the mixture control solenoid in the carb buzz/click. If it does, it means the ECM is awake, and the Check Eng. light should flash a code 12....one flash, a pause, and two quick flashes. It will do this three times, and then flash any other codes it has stored. Code 12 is just a nothing code..it only means the ECM is in diagnostic mode. If that's the only thing it flashes, it means there are no codes stored.
Then again...if the dadburn light stays ON ...there has to be an issue with the wiring.... Cry

Cry

CORRECTION! The 5 pin ALDL connector needs the D & E terminals jumped....my bad. Thanks Bob! Embarrassed

Embarrassed

|UPDATED|12/5/2013 5:20:14 AM (AZT)|/UPDATED|

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Re: Check engine light will not go off or flash (16/25)
12/5/13 9:43am

rraider1
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Woodland, WA - USA

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I don't want to confuse things but this GM ECM replacement paper says for 81 jumper D E

http://www.C3VR.com/member_pages/4201_4300/4221/ECM-test0001.jpg

http://www.C3VR.com/member_pages/4201_4300/4221/ECM-test0002.jpg

http://www.C3VR.com/member_pages/4201_4300/4221/ECM-test0003.jpg

http://www.C3VR.com/member_pages/4201_4300/4221/ECM-test0004.jpg

I hope I made the larger for those of us with older eyes

|UPDATED|12/5/2013 6:43:22 AM (AZT)|/UPDATED|

Re: Check engine light will not go off or flash (17/25)
12/5/13 8:20am

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Duncanville, TX - USA

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Embarrassed

Thumbs Up

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Joel Adams
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(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"

Re: Check engine light will not go off or flash (18/25)
12/5/13 7:46pm

stutrac
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Bethany, CT - USA

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1981

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Posts: 32

so am i to assume i jump the 2 on the left NOT the right to get the codes?

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Re: Check engine light will not go off or flash (19/25)
12/5/13 11:19pm

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Duncanville, TX - USA

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Here's what you need to jump... The black/white wire, and the White/black wire.... Thumbs Up

Thumbs Up

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Re: Check engine light will not go off or flash (20/25)
12/6/13 11:35pm

stutrac
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Bethany, CT - USA

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1981

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Thank you for the help everyone i got a code 15 coolant temp sensor, i see a few sensors on the block? location.

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Re: Check engine light will not go off or flash (21/25)
12/7/13 2:38am

rraider1
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Woodland, WA - USA

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I cant upload the picture using insert image I get an error

http://www.C3VR.com/member_pages/4201_4300/4221/1981-Temp-Sensor-Loc.jpg

Re: Check engine light will not go off or flash (22/25)
12/7/13 11:18am

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Yea!! So now we know why the light stays on! Clap

Clap

Check the connector for the temp sensor...they fail a lot. Here's Bob's pic.

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Re: Check engine light will not go off or flash (23/25)
12/7/13 11:30am

stutrac
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Bethany, CT - USA

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1981

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Posts: 32

for the cost i am going to replace it, since i am there i am going to change the T stat not sure if it is orig but it may be. thanks for the help Thumbs Up

Thumbs Up

what is the sensor on the right for near the header? i assume it is a oil pressure switch?

|UPDATED|12/7/2013 8:30:58 AM (AZT)|/UPDATED|

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Re: Check engine light will not go off or flash (24/25)
12/7/13 12:53pm

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Duncanville, TX - USA

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The sensor sticking out of the head, in between two spark plugs is the sensor for the temp gauge. The sensor in the intake is for the ECM. Thumbs Up

Thumbs Up

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Re: Check engine light will not go off or flash (25/25)
12/9/13 12:53pm

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Hope this helps ya

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