OBD 1 vs OBD 2 Harness

I am interested in having a guy cut down a wiring harness for my 1997 XJ buggy.

He normally does OBD1 harness', cuts them down to;
fuel pump, keyed, ground, 12v, etc, bare minimum

anyway I told him I have a '97, and we both questioned whether the older harness would work with the newer engine. Or how different the newer harness would be to cut down to accomplish the same hing.

So does anyone know if the sensors, etc will match up between the older - 97?

What are the major differences? Does this sound at all feasible?
Am I completely out to lunch with this idea?

thanks for any and all help.

beakie said:

I am interested in having a guy cut down a wiring harness for my 1997 XJ buggy.

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What is the benefit of this mod ?

If you plan to permanently drive in LIMP MODE and have no instrument cluster functions, you could use an OBD-I harness.


The plannned mod is pointless, and would lead to endless issues.

Tim_MN said:

What is the benefit of this mod ?

If you plan to permanently drive in LIMP MODE and have no instrument cluster functions, you could use an OBD-I harness.


The plannned mod is pointless, and would lead to endless issues.

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I have a a trail only buggy, no need for stock lighting, stereo, a/c, heat, etc.

I have thousands of little wires running all over the place... many of which I have already cut out (signal lights, interior lights, speaker wires, etc)

the point of the mod is to remove all but required wiring, less to think about, less to work around, less to worry about.

If I could cut out all but the required engine and tranny wiring to run the rig, I can wire in whatever else I need.

is it that hard to understand?

I've done it on a 94 harness, it's pretty easy. Reason was that I was swapping it into an 87 YJ that had separate harnesses for all the other stuff.

Keep the important stuff like the brake light switch, VSS, all the engine sensors, etc and you will be fine. Keep the CCD bus and required stuff to run your instrument panel as well. It's really pretty simple. Most of the extraneous crap is the same on the late model and early model, or at least similar.

Stuff you can get rid of, off the top of my head:
headlight/turn signal wiring
windshield washer fluid pumps etc
horns (might want to keep this though)
cruise control wiring
evaporative system if you don't mind the CEL being on - I would keep this stuff honestly
HVAC blower, speakers, stereo, power doors, power locks, etc

There isn't really that much to gain but I can see why you'd do it. I stripped it all out because the YJ chassis wiring already had all that functionality covered, so there was no reason to keep it in the harness for the engine controls, which was essentially a heavily stripped down customized XJ harness.

kastein said:

I've done it on a 94 harness, it's pretty easy. Reason was that I was swapping it into an 87 YJ that had separate harnesses for all the other stuff.

Keep the important stuff like the brake light switch, VSS, all the engine sensors, etc and you will be fine. Keep the CCD bus and required stuff to run your instrument panel as well. It's really pretty simple. Most of the extraneous crap is the same on the late model and early model, or at least similar.

Stuff you can get rid of, off the top of my head:
headlight/turn signal wiring
windshield washer fluid pumps etc
horns (might want to keep this though)
cruise control wiring
evaporative system if you don't mind the CEL being on - I would keep this stuff honestly
HVAC blower, speakers, stereo, power doors, power locks, etc

There isn't really that much to gain but I can see why you'd do it. I stripped it all out because the YJ chassis wiring already had all that functionality covered, so there was no reason to keep it in the harness for the engine controls, which was essentially a heavily stripped down customized XJ harness.

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Thanks for the info.
Like I said I've already rid most of the useless stuff from the firewall back, but not I am getting into wiring I am not comfortable cutting out. Stuff from the steering column area and into the engine bay.
If I could get a guy to strip a '97 compatible harness so I could just tear out the old n drop in the new it'd be ideal.

But it seems it may not be that easy.

Make sure he keeps the battery temp sensor, because without it the ECU/charging system aren't happy.

sidewaysstarion said:

Make sure he keeps the battery temp sensor, because without it the ECU/charging system aren't happy.

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is that for the 97 harness you mean? I am unfamiliar with the older OBD1 harness'


I am thinking I may have to skip this order, and go at it myself. Figure out what I can keep from the stock harness, and cut out the rest. If it's ECU or TCU, it stays. Get it running again, go about tracing wires, and if they are "extra" cutting them out.

Too bad there wasn't a ECU/TCU harness which just connected to the interior/exterior lights/accessories harness, if only they were thinking of these possible mods when they built them... 20 years ago.

From your question, it is obvious you do not understand all the CCD bus functions of the OBD-II wire harness.

Go ahead and cut off whatever you want, it doesn't matter to me.

Chill, man, it's a good question, especially for a buggy.

Beakie, if you have any questions about specific sections once you start digging into it, post up or PM me. I've got a 97 FSM somewhere or other (might be at a buddy's shop right now, I don't remember) and I can see my 98 FSM on the shelf from here, can look up wiring diagrams anytime they're needed.

Tim_MN said:

From your question, it is obvious you do not understand all the CCD bus functions of the OBD-II wire harness.

Go ahead and cut off whatever you want, it doesn't matter to me.

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wow, your grasp of the obvious is bang on.
thanks for, keepin it real!

kastein said:

Chill, man, it's a good question, especially for a buggy.

Beakie, if you have any questions about specific sections once you start digging into it, post up or PM me. I've got a 97 FSM somewhere or other (might be at a buddy's shop right now, I don't remember) and I can see my 98 FSM on the shelf from here, can look up wiring diagrams anytime they're needed.

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I have an '97 FSM here too, that's what I used to cut out what I have already. There were some I couldn't tell the difference/colours of, but new where the came from/went too... so felt ok getting rid of them anyway.
I will run what I have right now, and go deeper when the time comes... and may pick your brain a bit at that time. thanks for the offer.



Having spoke with the electrical guru again today he mentioned possibly switching to OBD1.
Get a manual trans ECM, maybe throttle body (MAP sensor?) most other sensors should swap. Would make for a simple buggy harness, without any of the OBD2 complications that I don't need in a strictly offroad ride.

I am going to hold off for now, need to spend $$ on getting everything else done, then will worry about this stuff. Everything worked when this project began, hoping for the same when the time comes to turn the key again... fingers crossed!!

If you switch to OBD1, no need to get a M/T ECU, the auto ones don't care, at all. I converted my 91 MJ from a 2wd auto to a 4wd manual and ran it from July 2011 till around April 2012 with the trans and NSS unplugged and the NSS bypassed (obviously, since they were on the back porch!) and then pulled the TCU as well while I had the lower dash half out to replace my steering column. Haven't seen a single CEL yet and it runs great.

I don't think it'll be necessary, you can cut off a decent amount even with OBD2. Sure, you still need stuff like the battery temp sensor (glad sideways mentioned that, because I completely forgot about it) but that improves the charging system performance/reliability, so I don't see a problem with it.

The dash wiring is a bit more confusing, but most of it is pretty easy to figure out. The vast majority of the instrument cluster is run by the two CCD bus wires, leave those alone, and the rest is well documented in the FSM. Leave the brake light switch wiring alone since the ECU does actually care about that, and you'll want to leave the VSS wiring in place as well as the ECU cares about that too, but most of the other stuff can be trimmed out. Basically what I'd do is unplug everything you don't need fro the harness, strip all the tape off, then you can pretty clearly see what sections of the harness become optional when you remove the connectors you don't need. Just make sure to pull any fuses that end up powering an unused lead, and make sure to resplice any grounds you cut in the process of paring the harness down.

If you stay OBD2 and want the check engine light to go out with a manual swap, there are people who can reprogram your existing ECU with a manual firmware image I believe. IIRC Talyn got his custom tweaked by christuned or something like that.

Great information thanks.
I have done much of what you advised... unwrapped, trace, remove, repeat.
Will mark and ensure I keep those vital ones, and try to update this thread in time with how things go.

Thanks