Jump ECM pins A and B 305 TPI runs fine???
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Junior Member
Joined: Oct 2008
Posts: 73
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From: Colorado
Car: 1988 IROC
Engine: 305 TPI
Transmission: BW 5-Speed
Axle/Gears: 3:73
Jump ECM pins A and B 305 TPI runs fine???
What does the ECM do when you operate the car with pins A and B are jumpered? With out them jumpered I get intermittent hesitation at take off through all gears, if I jumper A and B it runs great. SES seems to indicate that is is transitioning from Open loop to Closed loop after warm-up, but I'm still not sure what change jumpering A and B has on the ECM.
Supreme Member
Joined: Jul 1999
Posts: 5,183
Likes: 42
From: Oakdale, Ca
Car: 89 IrocZ
Engine: L98-ish
Transmission: 700R4
Re: Jump ECM pins A and B 305 TPI runs fine???
I think it put the ECM in "Feild Service Mode"...and disables several feedback functions from the sensors to the ECM to operate as designed.
So....when you jumpered A and B, before you start it, did you get any codes?
So....when you jumpered A and B, before you start it, did you get any codes?
Thread Starter
Junior Member
Joined: Oct 2008
Posts: 73
Likes: 0
From: Colorado
Car: 1988 IROC
Engine: 305 TPI
Transmission: BW 5-Speed
Axle/Gears: 3:73
Re: Jump ECM pins A and B 305 TPI runs fine???
I did get the codes. They were 21 (TPS Volt Hi, but it checks out ok), 33 (MAF (gm/sec HI) not sure how to test MAF and code 54 (which is fuel pump circuit) this has been changed and fuel pressure good. The engine runs no better/or worse if I disconnect the MAF. I've replace the MAF power and burn-off sensors with not change. Do you think the MAF is bad?
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