Weeding a 4.0 HO harness

[goldswim5]

Pulled one out of a cherokee today. I see the main engine harness unplugs from the ECM seperately, but what about the other harness that plugs into it? This one has the transmission controls in it and the plug for the coil packs, but is there anything else in it that's critical to the engine and trans running?

[SkooledMedic]

Originally Posted by goldswim5

Pulled one out of a cherokee today. I see the main engine harness unplugs from the ECM seperately, but what about the other harness that plugs into it? This one has the transmission controls in it and the plug for the coil packs, but is there anything else in it that's critical to the engine and trans running?

If you know what wires go to the sensors that are critical for the engine to run(TPS, MAP, IAT, O2, etc) you can probably weed out everything else. I'd leave the output wires from the PCM to the gauges unless you plan on going full custom aftermarket.

[Bansheestu]

Do yourself a huge favor. Do not remove or mess with the harness until you have the engine in the vehicle and fully functional. At that point remove things that you will not need.

[fantic238]

[ShmUDE]

when i swapped in my TJ 2.5 (yeah i know...) all i used was the engine harness and the harness that the computer plugs into that hangs on the back of the firewall. It has 3 big plugs on the drivers side that plug into the interior harness. Thats where i cut into it to grab the ignition stuff.

[Dirt-Fab]

I would recommend subscribing to AllData.com for the specific year/model of the doner vehicle. They have in my experience the most accurate and detailed wiring diagrams that are year specific. Last time I did one, it was like $30 for a year per vehicle. Well worth the money if you are going to go through a harness IMO.

[goldswim5]

Thanks guys. I think I'll be able to figure it out with those diagrams.

[Xjcrawler736]

What year are those diagrams from? I have a couple harnesses from HO motors and they are all a bit different. OBD1 or OBD2?

[fantic238]

Originally Posted by Xjcrawler736

What year are those diagrams from? I have a couple harnesses from HO motors and they are all a bit different. OBD1 or OBD2?

You are not reading. It says "Ignition coil n°1, 2, 3..." somewhere.

Ask yourself again: what year are those diagrams? is it OBD1 or 2?...

[kentuckytwostep]

um... those diagrams are for wrangler W/H layout... not XJ. XJ's don't have three plugs like that.

On XJ (4.0L w/AW4) OBD1 systems the main engine room harness has one large bulkhead connector on the driver side at the firewall, a large connector for the ECU, a grom that goes through to the TCU, two or three WtoW connections with the engine/tranny harness, an RB and a WtoW connection with the grille harness. On the other side of the bulkhead connection wires run to the IP and back to th back of the vehicle.

My TJ actually has all XJ wiring, engine and the AW4. I'm also researching how make a stand alone harness for just the engine/tranny... and also how to swap it over to aftermarket gauges so that I can get rid of the xj cluster that is zip tied to the dash bar of the roll cage.

[87manche]

Originally Posted by kentuckytwostep

um... those diagrams are for wrangler W/H layout... not XJ. XJ's don't have three plugs like that.

actually, the 2000 FSM manual I have here shows 3 connectors.
ad since the OP mentioned that it has coil packs it has to be an 00 or 01 donor vehicle.

and if you've used the OBD1 harness in your buggy the gauges are simple. OBD1 didn't have a can bus or anything that related to the ECM with the guages. So just swap out the gauge senders with aftermarket ones and hook up your aftermarket gauges. The ECM and the gauges were completely different senders.

[fantic238]

Originally Posted by kentuckytwostep

um... those diagrams are for wrangler W/H layout... not XJ. XJ's don't have three plugs like that.

No.

YOUR XJ harness does not have three plugs like that, because you are talking about the Chrysler SBECII (single board engine controller) MPI system, that was used from 1991 to 1996 on the l4.0 engine with a single 60 way connector.

[rockyota83]

Originally Posted by fantic238

No.

YOUR XJ harness does not have three plugs like that, because you are talking about the Chrysler SBECII (single board engine controller) MPI system, that was used from 1991 to 1996 on the l4.0 engine with a single 60 way connector.

the best years

[gavan]

Originally Posted by fantic238

No.

YOUR XJ harness does not have three plugs like that, because you are talking about the Chrysler SBECII (single board engine controller) MPI system, that was used from 1991 to 1995 on the l4.0 engine with a single 60 way connector.

1996 motors were OBD2, and different from the 91-95 motors.

I weeded out a 95 Cherokee harness to just the essential motor sensors and 2 relays. There is a lot of junk you do not need in the fuse box.

Like someone else said, get it running FIRST, then weed it out. Not having it start after you mess with it, and not knowing if it ever worked to begin with, is beyond frustrating.

[fantic238]

Originally Posted by rockyota83

the best years

I prefer the Renix system, based on Formula 1 technology of the first 80s, it is pre/OBD and it doesn't have a limp home mode. It was designed to perfectly work in open loop mode without an oxygen sensor (my '88 xj does not have one from the factory, neither a catalytic converter) and it has a self diagnostic feature that compares the measured values to preset limits: If the value sensed does not lie in these limits it is treated as defective and the ECU auto-generates known average values to determine injection pulse width and ignition timing.
The engine will still be fully operative with a malfunctioning MAP, MAT, TPS, Knock, CTS, OS and battery. Only CPS and camshaft positioner are essential to keep the engine running, maybe rough at idle, but fully operative at WOT.

[87manche]

Originally Posted by fantic238

I prefer the Renix system, based on Formula 1 technology of the first 80s, it is pre/OBD and it doesn't have a limp home mode. It was designed to perfectly work in open loop mode without an oxygen sensor (my '88 xj does not have one from the factory, neither a catalytic converter) and it has a self diagnostic feature that compares the measured values to preset limits: If the value sensed does not lie in these limits it is treated as defective and the ECU auto-generates known average values to determine injection pulse width and ignition timing.
The engine will still be fully operative with a malfunctioning MAP, MAT, TPS, Knock, CTS, OS and battery. Only CPS and camshaft positioner are essential to keep the engine running, maybe rough at idle, but fully operative at WOT.

I agree with you.

I loves the RENIX. You just have to have an understanding of how it works and you can make it run with nothing more than a multimeter and some bubblegum for the most part.

[fantic238]

Originally Posted by 87manche

I agree with you.

You agree with an asshole with no awesome? Wierd.

Three spare parts in the glovebox and you're good to go for 30 years on a Renix. A CPS, a fuel pump and a set of injector o-rings.

[87manche]

Originally Posted by fantic238

You agree with an asshole with no awesome? Wierd.

Three spare parts in the glovebox and you're good to go for 30 years on a Renix. A CPS, a fuel pump and a set of injector o-rings.

just because you're an asshole doesn't make your tech any less right.

I know people hate the Renix, I am a proponent. Just because the ECU doesn't self diagnose with nifty number codes does not make it harder to work on. probably easier actually, because you actually have to understand it and troubleshoot it properly instead of reading codes.