jeep 4.0 harness question - Pirate4x4.Com : 4x4 and Off-Road Forum

chimera_perpetua · 12-09-2010, 04:46 PM

I have a project I am working on that currently has a 258 carburated motor in it. I went to the junkyard today and picked up a computer,intake, exhaust, head and a bunch of other parts to swap a 4.0 head with efi on to my 258. I got the ecu from a different vehicle with the same motor because the one in the donor vehicle was gone. My question is are all 4.0 engine harnesses the same? I pulled the parts from a 94 grand cherokee laredo with a 4.0 and the ecu from a 95 cherokee with the same motor but the harness was in horrible condition so I figured I would buy one online. Are they all the same or do they differ between models/years for engine controls?

chimera_perpetua · 12-09-2010, 04:53 PM

also do I have to use a grand cherokee harness or can I use a harness from a tj?

tbrockey · 12-10-2010, 03:39 AM

I would go back and get the harness from the grand.

chimera_perpetua · 12-10-2010, 03:44 AM

I would normally do that but the harnesses in both donor vehicles are torn apart from other people at the yard. Also does anyone know what wires I can throw away and what wires I can keep?

Ghetto Fab. · 12-10-2010, 08:48 AM

You can probably use whatever harness you want to, however there may be some smog equipment changes and some of the connectors may be slightly different. My guess is that all the wiring is essentialy the same though. Like others have said, I'd try to find a harness out of a grand cherokee the same year as your motor to make it easy.

As far as what wires to keep, you need to keep everything thats critical to engine operation, and everything else can go. You need to get a good wiring diagram. I like to start at the computer and go through each wire one by one untill I know what every wire coming out of the computer does and label the ends if I can. I was able to eliminate 2/3rds of my junkyard harness in a couple hours by doing so. Most of that was lighting and body electrical junk.

Kevo

chimera_perpetua · 12-10-2010, 10:12 AM

thank you for the info, do you know where I can find a wiring diagram? Or where I should start looking? I appologize for my ignorance but this is the first time I have ever attempted something like this.

rer747 · 12-10-2010, 02:32 PM

Your best be would be get the factory service manual (FSM) for the year and model of Cherokee (XJ) or Grand Cherokee (ZJ) you are using as the donors. I got a 95 XJ and I posted a 95 ZJ FSM to http://www.workshopservicemanuals.com/. I do not know what was available for the 94 year.
You can search the site for the manual you want, but to download you have to register. I was leary, but so far it has worked out well for me. I got the manual I wanted and in a attempt to help others out, I posted the 95 ZJ FSM.

gearheadmb · 12-11-2010, 06:57 PM

Another thing you will find handy in a decent manual is called a pinout chart. It tells you what every pin at the pcm connector goes to in a simple list. Like a wiring diagram but it will speed up the process alot if you know what you are looking at and it will also be very handy in making a wiring harness work if it doesn't exactly match the engine and pcm.

half-cab · 12-15-2010, 05:21 PM

FWIW, my 6 cylinder '94 YJ is OBD-1, OBD-2 came in '95. The '94 OBD connection is under the hood. OBD2 ports came out under the dash.

12-09-2010, 04:46 PM	#1 (permalink)
chimera_perpetua Registered User Join Date: May 2009 Member # 136252 Posts: 39	jeep 4.0 harness question I have a project I am working on that currently has a 258 carburated motor in it. I went to the junkyard today and picked up a computer,intake, exhaust, head and a bunch of other parts to swap a 4.0 head with efi on to my 258. I got the ecu from a different vehicle with the same motor because the one in the donor vehicle was gone. My question is are all 4.0 engine harnesses the same? I pulled the parts from a 94 grand cherokee laredo with a 4.0 and the ecu from a 95 cherokee with the same motor but the harness was in horrible condition so I figured I would buy one online. Are they all the same or do they differ between models/years for engine controls? Last edited by chimera_perpetua; 12-09-2010 at 04:46 PM.

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12-09-2010, 04:53 PM	#2 (permalink)
chimera_perpetua Registered User Join Date: May 2009 Member # 136252 Posts: 39	also do I have to use a grand cherokee harness or can I use a harness from a tj?

12-10-2010, 03:39 AM	#3 (permalink)
tbrockey Registered User Join Date: Aug 2007 Member # 98110 Location: Maryland Posts: 36	I would go back and get the harness from the grand.

12-10-2010, 03:44 AM	#4 (permalink)
chimera_perpetua Registered User Join Date: May 2009 Member # 136252 Posts: 39	I would normally do that but the harnesses in both donor vehicles are torn apart from other people at the yard. Also does anyone know what wires I can throw away and what wires I can keep?

12-10-2010, 08:48 AM	#5 (permalink)
Ghetto Fab. Rock God Join Date: Jul 2001 Member # 6170 Location: Atascadero Posts: 1,017	You can probably use whatever harness you want to, however there may be some smog equipment changes and some of the connectors may be slightly different. My guess is that all the wiring is essentialy the same though. Like others have said, I'd try to find a harness out of a grand cherokee the same year as your motor to make it easy. As far as what wires to keep, you need to keep everything thats critical to engine operation, and everything else can go. You need to get a good wiring diagram. I like to start at the computer and go through each wire one by one untill I know what every wire coming out of the computer does and label the ends if I can. I was able to eliminate 2/3rds of my junkyard harness in a couple hours by doing so. Most of that was lighting and body electrical junk. Kevo

12-10-2010, 10:12 AM	#6 (permalink)
chimera_perpetua Registered User Join Date: May 2009 Member # 136252 Posts: 39	thank you for the info, do you know where I can find a wiring diagram? Or where I should start looking? I appologize for my ignorance but this is the first time I have ever attempted something like this.

12-10-2010, 02:32 PM	#7 (permalink)
rer747 Registered User Join Date: Sep 2010 Member # 169466 Posts: 1	Your best be would be get the factory service manual (FSM) for the year and model of Cherokee (XJ) or Grand Cherokee (ZJ) you are using as the donors. I got a 95 XJ and I posted a 95 ZJ FSM to http://www.workshopservicemanuals.com/. I do not know what was available for the 94 year. You can search the site for the manual you want, but to download you have to register. I was leary, but so far it has worked out well for me. I got the manual I wanted and in a attempt to help others out, I posted the 95 ZJ FSM.

12-11-2010, 06:57 PM	#8 (permalink)
gearheadmb Registered User Join Date: Dec 2010 Member # 175955 Location: Anna OH Posts: 85	Another thing you will find handy in a decent manual is called a pinout chart. It tells you what every pin at the pcm connector goes to in a simple list. Like a wiring diagram but it will speed up the process alot if you know what you are looking at and it will also be very handy in making a wiring harness work if it doesn't exactly match the engine and pcm.

12-15-2010, 05:21 PM	#9 (permalink)
half-cab Registered User Join Date: Jun 2005 Member # 48456 Posts: 25	FWIW, my 6 cylinder '94 YJ is OBD-1, OBD-2 came in '95. The '94 OBD connection is under the hood. OBD2 ports came out under the dash.