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Motorboatin' SOB, Headlight Cleaning Guru
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Discussion Starter · #1 ·
there are two thick wiring harnesses that run along both framerails and split up at the radiator support. i believe these harnesses are for the headlights, signals, etc. the driver side harness has the fusebox, battery wiring and maybe an o2 sensor, and the passenger side has a harness for the maf sensor and o2 sensor. are these two harnesses the exact same for the 3.8 and 5.0 engines?
 

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I have done the 3.8 to 5.0 swap. The harness that comes out of the firewall on the driverside by the master cylinder is the same. That is for your lights, wipers etc. The ECM harness that comes out on the passenger side firewall is the engine harness and is different for both engines. I just got the complete engine harness and ECM from a junkyard and it all fit great. I did extend the alternator wiring on the chassis harness if I remember correctly.
 

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my freind still might have one from a 91 5.0 car if your interested mike
 

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Motorboatin' SOB, Headlight Cleaning Guru
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Discussion Starter · #4 ·
i notice that the engine harness separates from the thicker harness coming out of passenger side firewall. im asking if that particular harness that runs up to the headlights, signals, etc is the same for both engines, and if the o2 sensor and maf sensor connectors are the same, as well. if they are different, then i have to pull that entire harness, which i want to avoid.

justin, i have access to a complete wrecked 5.0 bird. it was hit in the front, making it difficult to pull that entire harness, if its needed.
 

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year for year it is the same for the left harness but i cant answer that for the interchangabilty between years , the right harness is what controls the eec . the igntion module is in different locations between years as well .when i did mine i did the whole under hood harness to be safe .
 

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the eec part of the harness isnt a seperate harness, its as one,
 

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Motorboatin' SOB, Headlight Cleaning Guru
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6,912 Posts
Discussion Starter · #7 ·
well, i disconnected a big chunk of a harness that contains all of the connectors that physically plug into sensors, injectors, etc on the engine. i was left with a harness that has an o2 sensor and a maf sensor connector (and a few other connectors hear the firewall), which goes to a thick harness that runs along the framerail and splits off to the headlgihts and such. make sense?
 

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YES
it does , all teh ones i have ever seen are one big harness all the way into the car
 

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You could try just the engine harness piece of the ECM harness. Not sure if it will work though. I know the 3.8 and 5.0 ECM's are pinned different so the MAF, ignition module and such might not read with the old harness. I did the entire ECM harness to be safe and had no problems at all.
 
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