Parsnip

Hey all,
So recently i had an issue where my jeep died while driving down the road. it cut out once completely, then came back for a second, and died again. I already did a thread on it () and it is now at my godfathers garage. He told me that his scanner wasn't getting data from the engine comp, so my next thought is maybe the harness went bad or something...
apparently, when i had a *new* (100k miles) motor put in this, they grabbed one out of an 88 comanche, so basically what i want to know is do you guys have any idea of where i could get the harness if thats what it comes to, or if its something else, what the parts will cost me roughly?


thankks,
Preston

cruiser54

What year are you working on? Should fill out your profile or put it in your signature.

awsgrayrd

x2. Basic info is always a big help.

OBDII's was mass administered in 1995, but a few GM vehicles, in 1994, there was OBD 1.5, which was considered a combo of the two, but now a days, it is VERY difficult to find a scan tool for those vehicles. As of the 1996, all vehicle were required to have OBDII.

So the motor that you had installed from the '88 Comanche was definitely not set up with the technology. So from what I understand from your post you need to go to the jy and get everything from the back of the plugin under the dash and out!

Good luck! Hope its not too pricey for you.

V/r,
-Gray.

freegdr

theres no way to read any thing from renix model jeeps id check the wiriung to the cps for brittle/cracked areas touching grounding out.

Parsnip

I hope nothing is too pricey, I mean, I'm having my godfather work on it (he simply has more time on his hands to look around and such) and what he told me today is that its a wiring mess. Im just hoping maybe its a wire i didnt notice or its something simple, but the pain comes from the thought that it could be a bad harness totally...meaning id probably have to shell out a little more then i want :L

and i know you cant get a obd tester on it, i dont even think there was obd 1 then was there?

awsgrayrd

Yup, OBD was first introduced in 1969 with Volkswagon.

How long ago did you do the swap?

V/r,
-Gray.

cruiser54

Your harness is perfectly fine with the 88 donor engine and it's fuel injection system. Here's what I would do if it were mine, since you don't know if whoever switched the motors remembered to hook all the grounds back up:

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

acem

Actually you can hook up the Renix to the proper code scanner. You must have a DRBII or a good DIAGNOSTIC scanner. My friend has a SNAPON 2500 that hooks up to the Renix system. I don't believe the Renix system stores codes but you can use it to troubleshoot problems. Thx-Ace

cruiser54

That is true. The DRB has some tests you can do and you can read live data.

Do the grounds and verify they're all good first. It's something that needs done anyway and with bad grounds, many sensors send erroneous info to the ECU.

jeepsurfer1

Preston is a good friend of mine we replaced the icm, cps, distributer, coil, cap, wires, plugs, well I have a few days off comeing up and would like to stop by his jeep im going to check all grounds ( using this thread) anything else I should look for? Any thing in his remote unlock system? Anything besides the grounds? Thinks guys also its a 90 xj 88 mj motor auto trans, I wanna get it running for him beacuse he has helped me a lot with mine thinks guys

cruiser54

This:

I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals, and adding dielectric grease before plugging it back together. Be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.
ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then dielectric grease should be added before plugging them back in. I do this on every Renix era Jeep I purchase or work on for someone else.
Revised 03/15/2012

jeepsurfer1

Okay ill add it to the list I would love to.call him at work and tell him he has a running jeep ha ha well ill give it a try latter this week

jeepsurfer1

Question, I ran 10 awg wire to a switch near the CPU, if it would have hit the CPU for a period of time would be the cause of failure? It's so close to it it could have easily had a knee rested on it and push it into the pcm causing a short on the case problem? Also the 10gauge had no fuse on it... So yep...

jeepsurfer1

Okay its been awhile but we plan to work on it Friday after noon, if we don't then... Idk but the plan is to replace the harness and pcm and ill keep the old harness and rebuild it maybe...

jeepsurfer1

Done its runing quite well I must add, one pully has a bad bearing that squales but its all good,
Facts: the pcm was bad due to a switch grounded out on it, we checked every wire going to the pcm, harness is in good shape and I ran an extra ground strap, 2awg to the Rad support (pure copper)