Light when battery is good

DREAMOFMEMES

MEMBER
1991 CHEVROLET LUMINA
3.1L
V6
FWD
AUTOMATIC
130,000 MILES

Now before you screech "code 12 is not anything"! It is, and that is the only code I have gotten. What is code 12 and why does my car shut off when I start it? It does take like three seconds for it to drop the rpm's and shut off.

Tuesday, September 19th, 2017 AT 8:55 AM

6 Replies

JDL

MECHANIC
16,098 POSTS

It means no tachometer signal seen by the ECM. It makes sense, when you check codes it is usually key on engine off, no rpm's. Another reason, it lets you know the ECM is in diagnostic mode. You should always get the code 12 even when nothing is wrong.

As far as your problem, If you keep the throttle open, just a little, will it run? Usually with idle issues, I would want to check and clean idle air system. How long since a tune-up?

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Tuesday, September 19th, 2017 AT 10:13 AM

DREAMOFMEMES

MEMBER
3 POSTS

If I keep the throttle open just a little when it is on, it will not stall. The SES light is always on, but code 12 is the only code present. The car's been working ever since I got it, about three years ago, just fine.

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Tuesday, September 19th, 2017 AT 11:15 AM

JDL

MECHANIC
16,098 POSTS

I would probably remove the idle air control valve and see if it needs cleaning. You may need to clean throttle-body and those small passages.

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Tuesday, September 19th, 2017 AT 11:40 AM

JDL

MECHANIC
16,098 POSTS

I just wanted to add, if you remove IAC when going back, the pintle should not stick out more than 1 1/8 inches. You can usually work the pintle back with thumb pressure.

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Tuesday, September 19th, 2017 AT 12:29 PM

DREAMOFMEMES

MEMBER
3 POSTS

After an hour of finessing the battery, the car turned on, idled to stall, but restarted fast. I think something to do with the ignition coils, because it shuts off randomly sometimes.

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Tuesday, September 19th, 2017 AT 3:49 PM

KEN L

MASTER CERTIFIED MECHANIC
54,144 POSTS

Have you checked the fuel pressure when the engine stalls? You might have a fuel pump going out here is a guide to help you get the job done. If you don't have a gauge you can rent one for free at the auto parts store.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

and if the pump is bad here a guide that will give you an idea of what you are in for when doing the job.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Please let us know what you find.

Cheers, Ken

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Wednesday, September 20th, 2017 AT 1:08 PM