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Discussion Starter · #1 ·
1981 4.9 turbo, car will run with ESC not connected. Car recently purchased and found the computer was bad and replaced with a re-manufactured unit, after install computer shows a code 12 which indicates a no reference pulse.Not sure is this a normal code since the car has not been able to run with the computer and ESC connected at the same time. Installed a re-manufactured EST distributor. Seems like the only thing left is to replace the ESC and detonation sensor. Any thoughts on this problem? Thanks
 

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Have you timed it? I believe you are to ground a blue wire and then set the timing to 6 degrees before TDC. I think code 12 means the computer is working properly. If the esc detects a knock or predetination, it will retard the timing. If the timing is not right, it could prevent it from running. Does it seem to run good with the esc disconnected? No missing or strange noises like piston slap or a rod knocking?
 

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Code 12 is the "handshake" code that indicates no faults in system. At least on every GM computer I've ever tested.

Have you tested the esc wires for continuity. Also test for shorts. If any connectors are involved, make sure pins are not bent, burnt, or corroded.
 

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BillyMagg
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1981 4.9 turbo, car will run with ESC not connected. Car recently purchased and found the computer was bad and replaced with a re-manufactured unit, after install computer shows a code 12 which indicates a no reference pulse.Not sure is this a normal code since the car has not been able to run with the computer and ESC connected at the same time. Installed a re-manufactured EST distributor. Seems like the only thing left is to replace the ESC and detonation sensor. Any thoughts on this problem? Thanks
Yep, my computer is long gone off my 81 Esprit, 301, but no turbo, now a 350 out of a goat, a 74 Goat to be exact?? LOL
 

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Discussion Starter · #5 ·
Although the wires from the est connector to the esc were tested and seemed to be ok there must have been some low level noise in the wiring which is why the computer was showing code 12 which is a no reference pulse, ran 4 new wires and the car started up and ran good with no other error codes. Thanks all for your input. I am trying to keep this car all original as I can.
 
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