1984 check engine light problem
Thread Starter
Navigator
Joined: Dec 2012
Posts: 9
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1984 check engine light problem
I have a 1984 in Cali that will not pass smog because the light does not come on during start up. I replaced all of the bulbs in the cluster but still does not come on. During work I left the door open and the battery went dead. As I was charging it and trying to start the light worked. As soon as the battery was charged enough to start the car, the check engine light again will not come on.
Drifting
Joined: Jul 2012
Posts: 1,796
Likes: 14
From: Nampa Idaho
Wow, I never heard of that before? So they want your check engine light to come on when you have your ignition in the on position but not running? Sounds like you have a ground problem. Not sure if your check engine light is connected in the steering colum ignition or where, you will have to wait till an electrical expert chimes in!
Race Director
Joined: Aug 2007
Posts: 11,889
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From: Whitefish Falls Ontario
St. Jude Donor '08-'09
How are you running the battery down?? Is it running down on its own, or from you working on it?? If its running down because of an excessive draw on the battery you need to find this first.. Disconnect the negative battery terminal and connect a multimeter between the battery and the cable, IIRC you should not have more than 50 milliamps.. If more, start pulling fuses until it drops to the above range.. Your next investment s/b an FSM (factory service manual) because if you still have a CEL problem you need chart A-1 and access to the ECM to start back probing wires on its white connector.. 
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Le Mans Master
Joined: Sep 2006
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From: Phoenix AZ
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Sounds like the ECM is not providing the ground for the light.
GM designed the ECM so that the computer puts out a positive voltage looking for a ground so that if the wires ever grounded out, it did not burn out the ECM. The grounded wire would provide the mechanic a place to start. Since the cel is not coming on, I would start with volts at the aldl connector. if you have volts, it is probably the ECM. If not, the fuse might be bad. Then it could be the wire backed out of the ECM connector.
GM designed the ECM so that the computer puts out a positive voltage looking for a ground so that if the wires ever grounded out, it did not burn out the ECM. The grounded wire would provide the mechanic a place to start. Since the cel is not coming on, I would start with volts at the aldl connector. if you have volts, it is probably the ECM. If not, the fuse might be bad. Then it could be the wire backed out of the ECM connector.
Race Director
Joined: Aug 2007
Posts: 11,889
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From: Whitefish Falls Ontario
St. Jude Donor '08-'09
Before I ran a 12v wire, I would check pin E of the ALDL for ground, plus the gauges fuse for corrosion. If you don't have the ground on E then putting 12v on the cluster wont help..
Thread Starter
Navigator
Joined: Dec 2012
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If the ground was bad, would it work when the battery was down? If the battery is just strong enough to click the starter the light comes on and goes off as you turn the key. As soon as you put cables to charge the light goes out.
Race Director
Joined: Aug 2007
Posts: 11,889
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From: Whitefish Falls Ontario
St. Jude Donor '08-'09
I cant answer that, did you get a ground on pin E of the ALDL, did you check the fuse??
Race Director
Joined: Aug 2007
Posts: 11,889
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From: Whitefish Falls Ontario
St. Jude Donor '08-'09
There is a set of FSMs for sale in the parts for sale section...
http://forums.corvetteforum.com/c4-p...g-manuals.html
http://forums.corvetteforum.com/c4-p...g-manuals.html
Last edited by ccrazor; Jan 1, 2013 at 01:08 PM.
Racer
Joined: Sep 2010
Posts: 325
Likes: 7
From: Princeton Jct. New Jersey
It sounds like your battery is bad. Putting the charger on may just be masking this. If the problem persists after replacing the battery start chasing down the grounds, battery, engine block, ecm, etc.
Race Director
Joined: Aug 2007
Posts: 11,889
Likes: 8
From: Whitefish Falls Ontario
St. Jude Donor '08-'09
After further checking it appears that the pin "E" designation on drawing 8A-17 is incorrect, from both the ALDL pin out and another on page 6E2-8.
Both show pin "D" as going to the check engine light, this is where you should get the ground for the CEL from the ECM..
Both show pin "D" as going to the check engine light, this is where you should get the ground for the CEL from the ECM..