O2 harness install fail

Brando30

Member
Jan 4, 2019
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Ashland ky
Ordered replacement O2 harness from lmr. Got excited. Forgot to repin one of the wires (different on 90 compared to 91-93). Plugged in, started up. Obnoxiously high idle and engine light on. Remembered. Shut down, re-pinned, smooth idle, engine light on.

Tried running codes, when scanner is plugged in engine continuously revs. Took scan tool off, runs fine.

Did I fry short-circuit my ECU? If so, who makes a good replacement. Currently have a a9l, friend said I should run a9p.

Needing a second opinion.
 
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Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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Harness repin should match the ECU you are using. What transmission is in the car and what did it originally come with from the factory?

You can open the ECU and check the pin 46 trace and see if it's burned up. If it's not you should be good to go
 

Brando30

Member
Jan 4, 2019
34
2
8
39
Ashland ky
Harness repin should match the ECU you are using. What transmission is in the car and what did it originally come with from the factory?

You can open the ECU and check the pin 46 trace and see if it's burned up. If it's not you should be good to go
It's a a9l with a factory 5-speed.
Took pic of computer.
The other photos are from the instructions via the harness manufacturer.
 

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Dan02gt

10 Year Member
Mar 2, 2003
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Greenville, NC
The A9P is a auto computer. So you have the correct computer. It's very possible you burned out the dedicated pin 46 ground in the computer. It's a easy fix. You just need to pull the computer and check for burnt traces on the circuit board.
 
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Brando30

Member
Jan 4, 2019
34
2
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Ashland ky
The A9P is a auto computer. So you have the correct computer. It's very possible you burned out the dedicated pin 46 ground in the computer. It's a easy fix. You just need to pull the computer and check for burnt traces on the circuit board.
Easy diagnosis...how would I then fix it?
 
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