Can I use an automatic main engine harness to replace my manual main engine harness?

[Mike Patterson]

I've been chasing an Electrical Gremlin in my 2004 TJ. I've narrowed it down to being the Main Wiring Harness. My question is can I use a Harness from an 03/04 Automatic to replace my Stock Manual Harness? The Harness that I need to swap is the Harness that includes the Coil Pack, Cam & Crank Sensors Injectors, Etc.

I know that the Auto Harness has the additional Plus for the TCM and the Auto Trans. that would potentially be left unplugged. I'm assuming that something would need to be jumped for the Neutral Safety Switch but would that be it?

 

[Chris]

@mrblaine might know

 

[mrblaine]

I've been chasing an Electrical Gremlin in my 2004 TJ. I've narrowed it down to being the Main Wiring Harness. My question is can I use a Harness from an 03/04 Automatic to replace my Stock Manual Harness? The Harness that I need to swap is the Harness that includes the Coil Pack, Cam & Crank Sensors Injectors, Etc.

I know that the Auto Harness has the additional Plus for the TCM and the Auto Trans. that would potentially be left unplugged. I'm assuming that something would need to be jumped for the Neutral Safety Switch but would that be it?

I'll take a look at it today.

 

[mrblaine]

Best we can come up with is you'll have a bunch of unused connectors for the auto trans and you will need to come up with a reverse light and NSS circuit that are not present in normal "hook up to a manual" condition.

What gremlins are you dealing with that makes a harness swap easier? If you pull the harness, throw it on the driveway and go through it, the damage "should" be obvious unless it has been hackered up.

 

[Mike Patterson]

Best we can come up with is you'll have a bunch of unused connectors for the auto trans and you will need to come up with a reverse light and NSS circuit that are not present in normal "hook up to a manual" condition.

What gremlins are you dealing with that makes a harness swap easier? If you pull the harness, throw it on the driveway and go through it, the damage "should" be obvious unless it has been hackered up.

The Jeep sat for about a year(Needed a clutch and a few other things) and when I test drove it around the block, it felt like it had a Miss but had no codes. I figured I would try changing the plugs. I changed the plugs and now it idles good but once I go beyond 1800 rpm's, the engine sputters and the CEL Light comes on and throws the P0351, P0352 and P0353 or a combination of at least 2 of them.

I’m on my 3rd set of plugs, I’ve tried 3 different Coil Packs, I have now sent the PCM off(wranglerfix.com) to get checked. It checks out as Good. I’ve changed the Coil Pack Connecter, I’ve Changed the Fuel Injectors, Battery is Charged. The TJ has Fresh Fuel. I've also visually inspected the harness and I don't see any spots where it's worn through. I've done the "Jeep" Official Troubleshooting in reference to the codes. I just don't know what else to do.

 

[AndyG]

My first question would be did you see any signs of rodent activity in the engine bay.

Secondly , Your cam position sensor or it’s wiring could be suspect as well.

I can’t stress enough how meticulous you need to be in checking the wiring. You can’t tell by looking at it often- @John Cooper had a fairly serious issue and finally found it by feel- Running his finger across each individual wire.

These things have a lot of wires- above is an easy one to spot - if you happen to see it when you dig through the 30 wires or so in that leg.

I have a rig @mrblaine detailed a lot of things on- one thing that stands out is the attention he gave the harness. It told me this is a man who has seen all sorts of failure and has ideas on how to prevent it. I guarantee you “hey Blaine can you come over here” has been heard in Johnson Valley a few times.

 

[macleanflood]

X2 on ohm and continuity checks. I'd start with grounds, then do sensors especially cam and crank, then work my way to fuel injectors.

Check for 5v at the PCM and all the sensors too.

Watch Wes Work is a good YouTube channel out your way. He's fixed some pretty complicated wiring issues and might be interested in your problem for content.

Personally I wouldn't swap the harnesses. You're going from one problem to another and in addition to having to figure out how to make said harness work it's the same older wiring...and may have just as many issues as your harness.

-Mac

 

[mrblaine]

My first question would be did you see any signs of rodent activity in the engine bay.

Secondly , Your cam position sensor or it’s wiring could be suspect as well.

I can’t stress enough how meticulous you need to be in checking the wiring. You can’t tell by looking at it often- @John Cooper had a fairly serious issue and finally found it by feel- Running his finger across each individual wire.

View attachment 557918

These things have a lot of wires- above is an easy one to spot - if you happen to see it when you dig through the 30 wires or so in that leg.

I have a rig @mrblaine detailed a lot of things on- one thing that stands out is the attention he gave the harness. It told me this is a man who has seen all sorts of failure and has ideas on how to prevent it. I guarantee you “hey Blaine can you come over here” has been heard in Johnson Valley a few times.