Help diagnose my Check Engine light?
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Junior Member
Joined: Nov 2007
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From: Pennsylvania
Car: 1987 Trans Am
Engine: 5.0 L
Help diagnose my Check Engine light?
As far as I know and can tell, there is nothing wrong with the car at all. I checked the O2 sensor and it didn't appear to be faulty, the car isn't overheating, oil pressure is good, doesn't stall, everything appears to be fine! Any help diagnosing what could be "wrong" with my car?
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Joined: Mar 2009
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From: Des Moines, IA
Car: 90 Formula WS6, 86 Sport Coupe
Engine: 305 TBI, 2.8 MPFI
Transmission: 700r4, 700r4w/vette servos
Axle/Gears: 2.73 Open, 3.42 Open
Re: Help diagnose my Check Engine light?
The check engine light has to do with emissions stuff so your car will generally run fine when it comes on. If you take your car to advance auto they have a code scanner and will tell you whats wrong with it.
Alex
Alex
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From: Pennsylvania
Car: 1987 Trans Am
Engine: 5.0 L
Re: Help diagnose my Check Engine light?
I did, but they only have OBD II scanners, and most 3rd gen firebirds use OBD I codes/scanners
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From: Buffalo, NY
Car: 1988 IROC-Z
Engine: 427 SBC
Transmission: ProBuilt 700R4
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Re: Help diagnose my Check Engine light?
Copied from a Vader post:
Insert a tool as described above (paper clip) into the 'A' and 'B' terminals on the ALDL connector:
WITHOUT STARTING the engine, turn the ignition to the "RUN" position. Watch the Malfunction Indicator Lamp (MIL) - it will begin to flash. This is also commonly called the "Service Engine Soon" or "SES" lamp. The first code will flash three times, and will usually be a code '12'. This is encoded by one flash of the lamp, a brief pause, then two successive flashes of the lamp. Each code will repeat three times, so you should see a "Code 12" flash three times. Any other error codes will follow in numerical order, and each code should flash three times. After all codes have been displayed three times, the "Code 12" will again flash three times, then all other codes will follow as described earlier. This cycle will continue until the jumper is removed or the ignition is turned off.
After you have made a note of all error codes, turn off the ignition and remove the jumper immediately. If you forget to remove the jumper and attempt to start the engine with it in place, you could damage the ECM. For this reason you should remove it immediately.
WITHOUT STARTING the engine, turn the ignition to the "RUN" position. Watch the Malfunction Indicator Lamp (MIL) - it will begin to flash. This is also commonly called the "Service Engine Soon" or "SES" lamp. The first code will flash three times, and will usually be a code '12'. This is encoded by one flash of the lamp, a brief pause, then two successive flashes of the lamp. Each code will repeat three times, so you should see a "Code 12" flash three times. Any other error codes will follow in numerical order, and each code should flash three times. After all codes have been displayed three times, the "Code 12" will again flash three times, then all other codes will follow as described earlier. This cycle will continue until the jumper is removed or the ignition is turned off.
After you have made a note of all error codes, turn off the ignition and remove the jumper immediately. If you forget to remove the jumper and attempt to start the engine with it in place, you could damage the ECM. For this reason you should remove it immediately.
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From: Macedon, near Rochester, NY.
Car: 85 TA (sold), 88 Corvette, 02 Monte
Re: Help diagnose my Check Engine light?
I hope I don't get stoned for linking to a "rival site", but here's a list of error codes and a picture of which terminals http://www.austinthirdgen.org/index.php?pid=27
Thread Starter
Junior Member
Joined: Nov 2007
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From: Pennsylvania
Car: 1987 Trans Am
Engine: 5.0 L
Re: Help diagnose my Check Engine light?
I did as directed and put a paperclip in between terminal A and B (which I believe are the top right and the one to the left of it), but when I put the ignition in the on position, the "Service Engine Soon" light just stays on, like it would any other time. Any ideas as to why that could be? (possibly poor connection?)
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From: Pigeon Forge ,TN
Car: Firebird
Engine: 2.8 v/6
Transmission: t/5
Axle/Gears: open/3.42
Re: Help diagnose my Check Engine light?
Your light should go flash pause flash flash for a code 12 meening nothing is stored and the computer is functioning right so you may want to look into that light staying lit .
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Joined: Jul 2009
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From: Oregon
Car: 92 GMC Sierra 2500
Engine: 5.7l
Transmission: 4L70
Axle/Gears: GT4 3.73
Re: Help diagnose my Check Engine light?
Take note of where the little black tab is as shown on the following diagram and where this is on your connector. (So you are sure to be using the correct terminals...)
Thread Starter
Junior Member
Joined: Nov 2007
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From: Pennsylvania
Car: 1987 Trans Am
Engine: 5.0 L
Re: Help diagnose my Check Engine light?
Yeah, it's set up exactly like that, I was using the right terminals. But for some reason there are no metal connectors on the bottom row, and I believe the second on the left is also missing
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Joined: Jul 2009
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From: Oregon
Car: 92 GMC Sierra 2500
Engine: 5.7l
Transmission: 4L70
Axle/Gears: GT4 3.73
Re: Help diagnose my Check Engine light?
On mine, this is the connector under the steering wheel and the top row is the row closest to the driver.
Might try turning on the ignition, then briefly shorting the two connections. (As opposed to leaving it shorted).
Might try turning on the ignition, then briefly shorting the two connections. (As opposed to leaving it shorted).
Thread Starter
Junior Member
Joined: Nov 2007
Posts: 98
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From: Pennsylvania
Car: 1987 Trans Am
Engine: 5.0 L
Thread Starter
Junior Member
Joined: Nov 2007
Posts: 98
Likes: 0
From: Pennsylvania
Car: 1987 Trans Am
Engine: 5.0 L
Re: Help diagnose my Check Engine light?
This is an image of my terminal. I connected the top two on the right. Notice that most of them have no leads?
Junior Member
Joined: Jul 2009
Posts: 68
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From: Oregon
Car: 92 GMC Sierra 2500
Engine: 5.7l
Transmission: 4L70
Axle/Gears: GT4 3.73
Re: Help diagnose my Check Engine light?
As a double check, might want to see if you can read any codes with a code reader.
Otherwise, disconnect the ECM cable from the computer, then turn on ignition and see if the light is still on. If yes, then a short in the wiring or instrument cluster.
If off, then might indicate a problem with the ECM eprom or the ECM.
When getting much involved with problems such as these, it is best to follow the troubleshooting instructions in a GM factory service manual.
Otherwise, disconnect the ECM cable from the computer, then turn on ignition and see if the light is still on. If yes, then a short in the wiring or instrument cluster.
If off, then might indicate a problem with the ECM eprom or the ECM.
When getting much involved with problems such as these, it is best to follow the troubleshooting instructions in a GM factory service manual.
Thread Starter
Junior Member
Joined: Nov 2007
Posts: 98
Likes: 0
From: Pennsylvania
Car: 1987 Trans Am
Engine: 5.0 L
Re: Help diagnose my Check Engine light?
As a double check, might want to see if you can read any codes with a code reader.
Otherwise, disconnect the ECM cable from the computer, then turn on ignition and see if the light is still on. If yes, then a short in the wiring or instrument cluster.
If off, then might indicate a problem with the ECM eprom or the ECM.
When getting much involved with problems such as these, it is best to follow the troubleshooting instructions in a GM factory service manual.
Otherwise, disconnect the ECM cable from the computer, then turn on ignition and see if the light is still on. If yes, then a short in the wiring or instrument cluster.
If off, then might indicate a problem with the ECM eprom or the ECM.
When getting much involved with problems such as these, it is best to follow the troubleshooting instructions in a GM factory service manual.
Junior Member
Joined: Jul 2009
Posts: 68
Likes: 0
From: Oregon
Car: 92 GMC Sierra 2500
Engine: 5.7l
Transmission: 4L70
Axle/Gears: GT4 3.73
Re: Help diagnose my Check Engine light?
If the connector fit your connector, then that should have been the correct code reader. So that is a confirmation there might be a problem with the ECM or eprom.
Most important would be to get a factory service manual. This will tell you where various components are located which is the MOST important thing! (Where is that darn ECM located?)
First I would try removing the ECM connector per the factory instructions. These things are sensitive to static, etc., so best to read all the warnings and do everything step by step as it says.
You can order factory service manual sets from the following link or at a GM dealer.
http://www.helminc.com
FYI - I was just reading about the eprom data retention span being 20 years, maybe you are the first with this trouble?
https://www.thirdgen.org/forums/dfi-...tion-span.html
Most important would be to get a factory service manual. This will tell you where various components are located which is the MOST important thing! (Where is that darn ECM located?)
First I would try removing the ECM connector per the factory instructions. These things are sensitive to static, etc., so best to read all the warnings and do everything step by step as it says.
You can order factory service manual sets from the following link or at a GM dealer.
http://www.helminc.com
FYI - I was just reading about the eprom data retention span being 20 years, maybe you are the first with this trouble?
https://www.thirdgen.org/forums/dfi-...tion-span.html
Thread Starter
Junior Member
Joined: Nov 2007
Posts: 98
Likes: 0
From: Pennsylvania
Car: 1987 Trans Am
Engine: 5.0 L
Re: Help diagnose my Check Engine light?
If the connector fit your connector, then that should have been the correct code reader. So that is a confirmation there might be a problem with the ECM or eprom.
Most important would be to get a factory service manual. This will tell you where various components are located which is the MOST important thing! (Where is that darn ECM located?)
First I would try removing the ECM connector per the factory instructions. These things are sensitive to static, etc., so best to read all the warnings and do everything step by step as it says.
You can order factory service manual sets from the following link or at a GM dealer.
http://www.helminc.com
FYI - I was just reading about the eprom data retention span being 20 years, maybe you are the first with this trouble?
https://www.thirdgen.org/forums/dfi-...tion-span.html
Most important would be to get a factory service manual. This will tell you where various components are located which is the MOST important thing! (Where is that darn ECM located?)
First I would try removing the ECM connector per the factory instructions. These things are sensitive to static, etc., so best to read all the warnings and do everything step by step as it says.
You can order factory service manual sets from the following link or at a GM dealer.
http://www.helminc.com
FYI - I was just reading about the eprom data retention span being 20 years, maybe you are the first with this trouble?
https://www.thirdgen.org/forums/dfi-...tion-span.html
Thanks a lot, that will probably have to be my next step of action, so i'm just gonna have to wait for that service manual to come in! And about the retention span life: Yeah, that'd probably be my luck!
Junior Member
Joined: Jul 2009
Posts: 68
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From: Oregon
Car: 92 GMC Sierra 2500
Engine: 5.7l
Transmission: 4L70
Axle/Gears: GT4 3.73
Re: Help diagnose my Check Engine light?
BTW for older vehicles factory service manual sets may have 3 or 4 different books to the set. There might be a general service manual, an electrical diagrams manual, a fuel and emissions manual (engine and engine computer stuff), and a unit repair manual.
Newer vehicles might have everything integrated into a set of several books.
Anyway I find myself frequently flipping between the various books for the same problem. One might show the location of a device, another the wiring diagram, and another information for troubleshooting.
Newer vehicles might have everything integrated into a set of several books.
Anyway I find myself frequently flipping between the various books for the same problem. One might show the location of a device, another the wiring diagram, and another information for troubleshooting.
Thread Starter
Junior Member
Joined: Nov 2007
Posts: 98
Likes: 0
From: Pennsylvania
Car: 1987 Trans Am
Engine: 5.0 L
Re: Help diagnose my Check Engine light?
BTW for older vehicles factory service manual sets may have 3 or 4 different books to the set. There might be a general service manual, an electrical diagrams manual, a fuel and emissions manual (engine and engine computer stuff), and a unit repair manual.
Newer vehicles might have everything integrated into a set of several books.
Anyway I find myself frequently flipping between the various books for the same problem. One might show the location of a device, another the wiring diagram, and another information for troubleshooting.
Newer vehicles might have everything integrated into a set of several books.
Anyway I find myself frequently flipping between the various books for the same problem. One might show the location of a device, another the wiring diagram, and another information for troubleshooting.
Junior Member
Joined: Jul 2009
Posts: 68
Likes: 0
From: Oregon
Car: 92 GMC Sierra 2500
Engine: 5.7l
Transmission: 4L70
Axle/Gears: GT4 3.73
Re: Help diagnose my Check Engine light?
Well for my vehicles I have those too. Sometimes I need all the help I can get and it helps to get all the information I can. Sometimes the factory manuals go on and on about something and I can quickly look it up in the other manuals.
But to give you an idea of the information in the factory manuals, I have a 99 GM C/K truck with 4 books to the set and each book is 2 inches thick!
That's about 3,000 pages of information! And only on 1999 C/K trucks.
For a 92 manual, the electrical manual is 11 inches by 17 inches and about 300 pages long. All just electrical diagrams, layouts of harnesses, locations of each electrical device in the vehicle, connectors, where each connector is located, etc.
But to give you an idea of the information in the factory manuals, I have a 99 GM C/K truck with 4 books to the set and each book is 2 inches thick!
That's about 3,000 pages of information! And only on 1999 C/K trucks.
For a 92 manual, the electrical manual is 11 inches by 17 inches and about 300 pages long. All just electrical diagrams, layouts of harnesses, locations of each electrical device in the vehicle, connectors, where each connector is located, etc.
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