1986 Service Engine Soon Light
Thread Starter
Heel & Toe
Joined: May 2006
Posts: 15
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From: Inland Empire California
1986 Service Engine Soon Light
I have an '86 that has recently started having the Service Engine light come on intermittently. The light usually comes on when the car is first started and will stay on for the duration of the time it is running, but if the car is warmed up and I start it the light does not come on. The vehicle does runs great regardless of the light. I was wondering what the problem might be, I was told that it maybe the EGR Valve but what do you guys think. Thanks for your help!
Le Mans Master
Joined: Feb 2006
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From: Louisiana
Get a paperclip. Make it into the shape of a U. Find the ALDL under the driverside dash and insert one end of the paperclip into terminal A and the other in terminal B (two most upper terminals). Turn the key to the "on" position. The SES light should start flashing. It will flash a code 12 (one flash, pause, two flashes, pause....x3). The next set of flashes will be the code(s) stored. Make sure it flashes a code 12 again before turning the key "off". Remove the paperclip.
When the ECM is in diagnostic mode the main fan will run along with various sensors and relays.
Tell us what you get.
When the ECM is in diagnostic mode the main fan will run along with various sensors and relays.
Tell us what you get.
Thread Starter
Heel & Toe
Joined: May 2006
Posts: 15
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From: Inland Empire California
Are the A and B terminals in the upper left or right? Where will the SES light flash, and will the code(s) I'm looking for just be a series of flashes. Finally the code 12 will be one flash, pause, two flashes, pause, one flash, pause, two flashes, pause,one flash, pause, two flashes, correct? Thanks.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
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From: Louisiana
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Are the A and B terminals in the upper left or right? Upper right.
Where will the SES light flash, and will the code(s) I'm looking for just be a series of flashes. On the DIC, where the service engine soon light comes on among others. Yes, you will need to pay attention and count the times they flash and it always repeats itself times 3.
Finally the code 12 will be one flash, pause, two flashes, pause, one flash, pause, two flashes, pause,one flash, pause, two flashes, correct? yep.
Where will the SES light flash, and will the code(s) I'm looking for just be a series of flashes. On the DIC, where the service engine soon light comes on among others. Yes, you will need to pay attention and count the times they flash and it always repeats itself times 3.
Finally the code 12 will be one flash, pause, two flashes, pause, one flash, pause, two flashes, pause,one flash, pause, two flashes, correct? yep.
Team Owner
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From: Summerland B.C. Canada
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Instructor
Joined: May 2005
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From: MESQUITE TEXAS
check engine light
hello i have a 1985 vette with the tune port i tried to pull the codes with the paperclip but all my car did was flash the check engine light 30x did do something wrong or did not throw codes when the check engine light came on.
Thread Starter
Heel & Toe
Joined: May 2006
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From: Inland Empire California
Ok, I gave it a try today and I got a code 32 (three flashes, pause, two flashes . . . x3), the EGR code. So where should I start, what is the most likely culprit, the valve, solenoid, diagnostic switch . . . Thanks for all your help so far!!!
Team Owner
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From: Phila., PA burbs
Intermediate
Joined: Nov 2004
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From: Mt Vernon IL
My Check Engine Soon light was acting strangely for the past couple of weeks, too. I left it with the Chevy dealership overnight so they could do a cold start the next morning. They noticed that the cooling fan came on with the cold start, which made them suspect the ECM itself. They did a 'tap test' on the ECM unit and the engine went spaz on them. They found a new ECM in a nearby Chevy dealer, installed it, and it seemed to fix all the other quirks. They told me to test it for a couple of days. I did, and it is behaving great. Just another option- something to look for.
Instructor
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From: Deep in The Heart of Dixie
Team Owner
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From: Summerland B.C. Canada
Le Mans Master
Joined: Feb 2006
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From: Louisiana
Just follow this link the Agent posted. You may have to read through it a few times but it will lead you to the problem. Could be the solenoid, EGR (usually the diaphram not holding vac), switch, wiring, wiring/vacuum connection, or ECM itself.
A vacuum guage and a VOM will come in handy.
Team Owner
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Sometimes you'll get false positive codes. So remember to clear the codes and drive it again. If the code reappears then start troubleshooting.
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
If the code reappears then start troubleshooting.
If the code 32 comes back there is a diagnostic method on my site that will help you pinpoint the problem component in the EGR subsystem.
Le Mans Master
Joined: Feb 2006
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From: Louisiana
To clear the codes...disconnect the neg side of the battery for ~30 seconds or pull the ECM fuse. This will erase anything learned in the ECM as far as fuel trims, ect. They will have to be relearned, but barely noticable to us.