Revised 3/6/2014
As noted in Tip #2, Renix C101 Connector Refreshing, in 1989 the factory wiring harness no longer included the problematic connector. For a long-term fix that will avoid many problems in the future, it is a good idea to just get rid of the thing entirely.
A helpful video can be found in the link below:
Unbolt the 2 halves of the C101 using a ¼” socket. On each half there is a plastic cover where the wires enter. They are removable but you’ll probably end up busting them off. Lightly bolt the C101 back together, away from the firewall. Peel back the split-loom covering from the body side of the C101 connector down to where the harness splits and goes toward the firewall, pretty much below the MAP sensor. On the engine side, remove the split loom about the same distance.
Now you can see from one side of the C101 to the other. Beginning at the top row, closest to the motor, be absolutely sure you cut the matching wires on each side of the connector off to about 1/2 inch. This will allow you to verify the original position of each wire color in case of mistakes or confusion. CUT AND SOLDER ONE PAIR AT A TIME. The wires may be wound a bit in their looms. See the first photo. Get them unwound neatly and do the following, ONE AT A TIME.
Slide your shrink tube over one wire. In a well ventilated area, solder the wires together and then slide the shrink tubing over the solder joint. Heat the shrink tubing so it seals your completed solder joint. Keep going until you’ve done all 22 or so connections.
Both sides of the C101 connection have a wire that is brown with white tracer. Follow each of these wires back until you come to a point where three wires are crimped together.
What you want to do here is cut the crappy factory crimp out of each set of three and bring both sets of three wires together and solder them together, using shrink tubing as well. All 6 wires. These particular wires will not end up in your normal C101 elimination loom. The sensor ground upgrade is found in Tip 6.
After all the soldering and shrink tubing is done, bundle the wires together in a new piece of 3/4″ split loom. Tape it up and secure it to the C101 connector’s original bolt hole or somewhere else along the firewall so it will be protected.
Revised 01-31-2016
What’s up Cruiser! Nice site, I came over from Cherokeeforum. Im having problems with my ol girl. She’s lagging in & out of power on acceleration. It is also noticeable in Neutral & park when I rev up. I’ve cleaned the C101, IAC, & a lot of connections. I’ve replaced the CPS, Fuel Filter, O2 sensor, Plugs, Cap & Rotor. Vac lines checked & replaced as needed. I replaced the fuses under the dash. I put Fuel injector cleaner in with a full tank….it stopped for the majority of the tank then came back. Its getting noticeably worse. Also While I was replacing fuses I found a wire with a plug for a fuse. That wire comes from the same place as the Ignition wire that plugs into the fuse panal. What size fuse do I put in? I can’t find it online at all.
I’m assuming this is an 87 or 88 with a 4.0 since you mention a c101 connector.
You could very well have some faulty injectors given that the symptoms disappeared for a period of time after adding injector cleaner to the fuel tank. Have you changed the fuel filter since then? If it’s old and has never had it’s injectors replaced, I recommend the volvo 746 injectors. They are available from Programbo on Cherokee forum. I’ve used a few sets of his and the results were great.
I was hesitant about tackling this one, but I freshened up my soldering skills and decided to tackle it. I cut and spliced one at a time like you recommend, but I ran into a couple of issues. First of which some of the wires were faded out and the coloring was very hard to decipher. To counter this issue I referenced each wires place in the connector on either side before i spliced them. Even after making every attempt to do this correctly I seem to have made a mistake somewhere along the way. The engine will crank and run for a minute or two and then bog down and stall out. This issue was not present before I spliced the harness. I have removed all the covering to ensure the wiring was done correctly and noticed that a couple wires are different colors on either side of the connector. Do you have a workaround for correcting any mistakes made during this process such as a wiring diagram including wire colors and locations inside the connector? I still have the old C101 and can reference back to it to a certain degree but the fading in the wires coloration has been problematic.
Check this first. Did the hose from the MAP to throttle body get damaged in any way during this process?
I don’t have a good diagram to guide you nor a used C101 kicking around.
solution– use your ohm meter and find the wires on the c-101–on each side the discoloration of the wires can be seen. most of mine were the tan wires and a blue wire. using the Ohm meter and going one wire at a time i did mine and no errors.
So I’m in the process of doing this right now and I’ve discovered that there are a couple wires on the engine side that don’t have corresponding wires on the firewall side. They are not the sensor grounds. I’m not sure what I should do with them? Should they connect to something important? Help!
No worries. Just leave them. Make sure the ends are insulated from grounding.
hey cruiser ive done a lot of your tips and i sure appreciate all your input on the net.
question: i have the negative probe on the battery the lead wire in the middle B terminal of the tps connector that gives 1,5 ohm after wiggling the c101 connector on my xj 88 the ohm varies up to 2.8. i read you said closer to 0 ohm better it is of course 🙂
but what is close enough to be concidered ok? 1.5 is ok ? 2.8 is bad ?
thank you for all your help
Marc, it’s not THAT high, but less than an ohm is best.
Have you cleaned the c101 yet?
Cruiser54 I recently got an 88 comanche and need all the help I can get could you call me sometime 8702131511.
Email me at cruiser54private@gmail.com
thanks for your reply, yes last summer i cleaned the c101 all out and you were right its full with some kind of tar, cleaned it all out but never did the ground test as you mentioned it looked pretty good, so now again this summer i decided to open it up and give it another clean after i had messaged you i got the test done again and the ohm stays at 1.5 down to 1.3 cant seem to get it any better but at least it doesnt vary anymore. i would like to do the elimination aswell but not soon perhaps next summer. im working my way through all your renix tips in a different order but sure are eliminating a lot of problems, thanks again 🙂
hey cruiser54
to find the crappy crimps only without doing the c101 connector elimination. as those hiden in the wire tree ? do i have to take the wrap off to find these.. im having hard time find this
thank you again, marc
performed this today, thanks for all of the tips! It went smooth!
Hi Cruiser, I a about to embark on this in hopes of better economy but have no dug in at all. Is there a reason for removing some of the excess wire going to and coming from the connector. There looks to be a considerable excess. It would be farther under the hood and thus harder to reach plus there may not be a loop to absorb any length. Anything else
Make that “not removing excess wire”
Your choice. My back gets sore enough when leaving the loop. LOL.
Check out the new video attached to this Tip. Let me know what you think.
I am going to do this asap , when my 88 keep idles it seems to lunge forward then seems to wanna die out sometimes it does others it does not. I’ve changed fuel pump fuel filter and all injectors sensors and it still does it..I can’t get a read on my tps. When I start it up it runs fine but if I shut it off and wait a few minutes it’ll start up but run or idle poorly and spit n sputter n backfire then it takes a while to clear up . Seems like if it’s flooding out some how. My fuel pressure is at 20 psi when I remove vacuum line it does not change any when I pinch return line the pressure drops… any suggestions would be more than greatly appreciated oh yea my cruise control does not work an my wipers work real slow .
Have you performed Tips 1 through 5?
Although you replaced the fuel pump, there are some real junky pumps being sold out there. Airtex and Carter are the biggest offenders.
I have not doneanything yet we just got bombed with massive wind and rain storms cause of the hurricane in the texas coast plus starting new job. i got the new ground straps and am going to eliminate the c101 box and go from there. the ful pump i installed is a carquest brand which is actually putting out about 7psi less than what was in it before…thnxxx for the reply i’ll let you know what happens as soon as i get a chance to work on it again we are expecting rain for another week or so and i do not have the room to put it in my garage at this time thnnxxx again…
Good plan. Stay safe and dry.
Just to let you know i finally got rid of the 101 box but that did not fix my problem ..after further research and trial and error it was $10.00 part which was the FUEL PUMP BALLAST RESISTOR sitting by the air box..I bypassed it with a jumper wire and like magic i got my fuel pressure to specs no stalling or stumbling or backfiring…It starts and restarts no problemo so i have some on order just to have extras not sure if it can be eliminated permantley but i appreciate all the help oh and i also did the ground wire improvemnts which i’m sure all combined it’s kickin some butt again thanxxx again for all the help and info…
It can be eliminated. It’s only there to reduce fuel pump noise.
ok good to know . it’s running like a champ now..i love driving this old jeep get a lot of thumbs up i liketo old school stuff always wanted one but could never afford one. also now i can concentrate on my 84 k5 blazer just rebuilt a strong 350 went all out just need to fine tune and button up..thnxxx again for all the info
Is there a write up on bypassing the “fuel pump ballast resistor”? I just picked up a pretty clean 87 XJ Wagoneer as my daily, its my first Renix, and I’m sure I’ve been to your sight every day since. Doing Tips 1-5 this weekend. Thanks.
No write up on that, but you basically unplug the wire from each end and make up a jumper wire between the 2 wires you disconnected. Good luck with the Tips!! Be thorough.
Thanks for the reply. Turns out my 87 Wagoneer dose not even have one. It was confusing until I learned that they put them in later. I am in the process of upgrading all the battery cables/grounds to #2 awg. After that I plan to delete the C101 and install the Volvo injectors (also need to replace the cracked exhaust manifold and O2 sensor while I’m at it). I look forward to reporting back (hopefully with a smooth running renix). Thanks for all the knowledge you have made available!
You’re very welcome!!
Hello cruiser54…Chris Garcia again ..i am having same problem with my 88 cherokee as before when at idle the whole vehicle surges forward then will shut off sometimes it restarts other times it takes 5-10 minutes before restart and only at idle not when running down thw street or highway speeds .. i have eliminated the c101 box even went thru an recut and resoldered all wires and did the ground up grade it’ll do okay for a day then do the same thing has new injectors pump rgulator sensors everything .. now just totaly fustraded and lost on what to do next even eliminated fuel pump ballast…the only thing i’ve noticed since i’ve had this vehicle is where all the relay go to that one area someone put all butt conectors on every wire would that have anything to do with the same problem over nad over..need help please
Chris, you sure have stuck with it.
YES. Eliminate all the butt connectors. Solder and shrink tube.
ten four sir when i get some time i will do that also…
Cruiser54
I understand the elimination of the connection. I have a 1988 comanche Pioneer 4.0l, and it is running pretty good , but the wiring under the hood is hideous! Bought it last November and have been making headway.
Could you explain in a little more detail about matching the wires from the two connections, especially if the other side has none, or if the colors are different.
Trying to be brave
Pfran43185@gmail.com
Thanks
Yes.
Just match them from one side of the connector to the other one by one. Disregard colors or missing wires.
I am currently doing a 2.8 to 4.0 Renix swap. I have the entire Renix harness out of of the donor vehicle. I suppose NOW would be a better time to do this, rather than while the harness is in!
certainly. What an opportunity!!!
Well, after 2 soldering irons, and finally getting a gas powered iron, I finally got this job done! I have done quite a few of these tips (grounding, etc.) So far everything runs okay (Still haven’t driven it). I still have a few more of the tips to do, but I am taking my time. And thanks Cruiser for putting up with my emails. As you know, I had a couple of scares with “same color” wires on the TCU harness.
Finally did this today after watching the video last night. I now feel kinda dumb for spending all the time cleaning it I did previously. I believe I spent more time cleaning it then it took to delete it. With this done I can finally say I made it through all the tips. Thank you Cruiser fire all the wonderful tips. My truck is back to life beacuse of this website.
Thanks for the kind words. YOU did it!!!!!!
Without your efforts it wouldn’t have gotten done.
I was wondering if you could help me understand Renix fuel trim. We are discussing it on the Comanche Club and no one has a real answer. My LTFT is 91 is that rich or lean?
IIRC, 128 is the base number for fuel trims. So, 91 means it’s pulling fuel. As in rich.
The MAP sensor plays the biggest part here. Make sure your intake manifold bolts are snug. . Inspect the tube to the MAP from the throttle body. There’s a Tip for that…
What’s your STFT?
Have your fuel trims changed since eliminating the C101? That would be nice to know.
STFT starts at 128 and goes down from there. MAP hose tip is done. I have a 88 4.0. It has 746 injectors, bored throttle body, 90 ECM, and all your tips done except the CPS moo. The C101 delete didn’t change anything. It was at 91 I unhooked the battery to do the delete. After I was done with the delete it reset to 128, took it for a 40+ minute drive and LTFT is back at 91. The intake/exhaust manifold bolts have been tightened.
Are your ST and LT trims the same?
CAn you take the engine compartment wiring harness from a 89MJ and install in a 88 by just plugging it into the firewall?
Not that easy unfortunately.
I am also curious about using a one piece harness. I have the c101 on my Cherokee but I have a full one piece harness from a 88. Is there any reason I hadn’t pull one out and swap the other in?
an 88 would have the C101 connector. 89 and 90 didn’t. I’m sure it can be done, but I’m gonna bet you will run into differences.
I have recently discovered your website and “The Holy Grail” of Renix information, I just did this on my 88 Cherokee and he runs like new again!
I love it!!!