I apologize, didn't finsh my coffee this morning. Code 12 is the normal flash (flashes 3 times after its initialized) going into diagnostics. Any stored codes will follow.
Bad ECM 1985?
Thread Starter
Instructor
Joined: Apr 2013
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Bad ECM 1985?
Hi i bought an 85 to restore and im having trouble with the computer.When its running it shows the check engine light and the light gives a code 12 when its running.When I jump the diagnostic connector to read the codes it just gives me the code 12 over and over.Could it be a bad ecm?
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
Hi i bought an 85 to restore and im having trouble with the computer.When its running it shows the check engine light and the light gives a code 12 when its running.When I jump the diagnostic connector to read the codes it just gives me the code 12 over and over.Could it be a bad ecm?
Safety Car
Joined: Apr 2011
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CODE 12 IS NOT related to the EGR...
Code --12 is the system announcing -> SYSTEM NORMAL<-
You are supposed to see 12 12 12 space 12 12 12 when the system is operating as it should. ALCL jumpered. There will be a stored (if any or several) DTC in the 'space' between the 3 code 12s.
if your SES is on even without a jumper in the alcl then you have something shorted or crossed. If there are no codes stored, its shorted. try a known good ECM to test.
you cannot diagnose an EFI computer car without the correct FSM for that car. Too many codes, too many systems that require exact adjustment.
Code --12 is the system announcing -> SYSTEM NORMAL<-
You are supposed to see 12 12 12 space 12 12 12 when the system is operating as it should. ALCL jumpered. There will be a stored (if any or several) DTC in the 'space' between the 3 code 12s.
if your SES is on even without a jumper in the alcl then you have something shorted or crossed. If there are no codes stored, its shorted. try a known good ECM to test.
you cannot diagnose an EFI computer car without the correct FSM for that car. Too many codes, too many systems that require exact adjustment.
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
If the CEL is on when the car is running and only code 12 appears when you pull the codes, something is wrong. If code 12 is the only code, no CEL should be lit. You have something shorted or crossed somewhere.
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From: Merritt Ils Fl
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From: Rockwood TN
Okay, this looks like a decent place to but in...I've also got an 85 I'm trying to get on the road again, but I'm in a little over my head in some ways.
It ran when I got it, then the auto trans went out. I bought a working manual trans, and almost all the bits and bobs to get it in, but I want to check that I don't need a new ECM to have it run right..... I know I'll need a new wiring harness for the trans, and I'm planning to get a new engine harness too cause it'll be nice to have an unbutchered one, but I don't know about the computer.
Any thoughts are appreciated, and thanks for reading
It ran when I got it, then the auto trans went out. I bought a working manual trans, and almost all the bits and bobs to get it in, but I want to check that I don't need a new ECM to have it run right..... I know I'll need a new wiring harness for the trans, and I'm planning to get a new engine harness too cause it'll be nice to have an unbutchered one, but I don't know about the computer.
Any thoughts are appreciated, and thanks for reading
Melting Slicks
Joined: Aug 2011
Posts: 2,844
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The engine will run on with the automatic prom. Idle speed will be effected. You can have a prom programmed at tunedperformance.org
or a better option is use a 86-89 harness and upgrade the slow baud rate 870 ecm to a 1227165 ecm.
or a better option is use a 86-89 harness and upgrade the slow baud rate 870 ecm to a 1227165 ecm.
Melting Slicks
Joined: Aug 2011
Posts: 2,844
Likes: 176
You can ground the p/n switch orange/black stripe pin b10 at your ecm. This might get the idle to 6-650.
timing curve and fueling is slightly different as well. But many have run man trans on automatic calibration.
timing curve and fueling is slightly different as well. But many have run man trans on automatic calibration.
Last edited by Tunedport90; Oct 4, 2019 at 09:31 PM.