Check Engine Light resetting itself
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Joined: Sep 2007
Posts: 77
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From: Richmond VA
Check Engine Light resetting itself
I have a 1991 Corvette auto. It is completely stock.
The check engine light comes on everytime I drive it after about 20 minutes or so.
When turning the car off the check engine light resets itself everytime which is preventing me from reading the code. This results in a code 12 everytime.
I have no idea what is going on and it's definitely annoying. The car itself is running smoothly and doesn't appear to have anything wrong. I was thinking it could just be emissions.
I searched this forum and I googled with no success.
Thank you in advance.
The check engine light comes on everytime I drive it after about 20 minutes or so.
When turning the car off the check engine light resets itself everytime which is preventing me from reading the code. This results in a code 12 everytime.
I have no idea what is going on and it's definitely annoying. The car itself is running smoothly and doesn't appear to have anything wrong. I was thinking it could just be emissions.
I searched this forum and I googled with no success.
Thank you in advance.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
Given your situation the way I would approach this is to connect my Tech 1, drive the car and when the light comes on look for a code with it. If you don’t have that kind or similar unit, you may have to go to a corvette shop and have them connect their scanner while the engine is running and before you shut it down.
Having said all that, I would normally think if a code was set as indicated by the check light that the code should be set as a historical code.
Not that completely familiar with the 91 on board diagnostics and not sure if you have a speedometer display or just get the codes with the flashing lamp. Just food for thought.
Having said all that, I would normally think if a code was set as indicated by the check light that the code should be set as a historical code.
Not that completely familiar with the 91 on board diagnostics and not sure if you have a speedometer display or just get the codes with the flashing lamp. Just food for thought.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
My 87 had a similar problem, if I remember right it was an EGR switch.
But the best thing is to get it on a scanner as mentioned. I also seem to remember someone else that ended up with a bad CTS, seems he said the computer corrected for it before it could actually throw a code.
But the best thing is to get it on a scanner as mentioned. I also seem to remember someone else that ended up with a bad CTS, seems he said the computer corrected for it before it could actually throw a code.
Thread Starter
Advanced
Joined: Sep 2007
Posts: 77
Likes: 0
From: Richmond VA
Thanks for the responses.
The car is OBD1 and used the flashing CEL to indicate what the code is. There is also another method I haven't tried where you can put a jumper between the A and B terminals to have the CEL flash and get the code.
I just did a quick search on Tech 1 (google) and didn't find anything. Is that something that is safe to leave hooked up to the car when driving? No clue how people tune the factory chip but could this be another alternative? Have a tuner hook a laptop up?
I'm just throwing stuff out there so I am probably off.
The car is OBD1 and used the flashing CEL to indicate what the code is. There is also another method I haven't tried where you can put a jumper between the A and B terminals to have the CEL flash and get the code.
I just did a quick search on Tech 1 (google) and didn't find anything. Is that something that is safe to leave hooked up to the car when driving? No clue how people tune the factory chip but could this be another alternative? Have a tuner hook a laptop up?
I'm just throwing stuff out there so I am probably off.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
The A,B on the ALDL is the place for you to start. With the key off use a jumper wire or paper clip jumping A&B they're the top two right hand pins. After that turn the key ON, but don't start it. The CEL will flash like this, flash, pause, flash,flash. That indicates a code 12, it should do this 3 times, then if a code has been stored it should flash the code, for instance, flash,flash, flash, pause flash,flash, flash,flash, would indicate a code 34, it should repeat itself 3 times, then the code 12 again....unless there is more than one code, if that's the case it would follow the code 34 I described. And I just pulled 34 out of the air as an EXAMPLE only.
I wouldn't run the car while this is connected.
You don't need a tuner. I purchased a used laptop, bought a cable from Moates, down loaded Tunerpro RT ( a free program) and can watch all the functions (sensors etc.) very nice tool to have. I think my total investment was about $200. including the used laptop.
I wouldn't run the car while this is connected.
You don't need a tuner. I purchased a used laptop, bought a cable from Moates, down loaded Tunerpro RT ( a free program) and can watch all the functions (sensors etc.) very nice tool to have. I think my total investment was about $200. including the used laptop.
Last edited by rick lambert; Sep 23, 2008 at 12:54 PM.
