C101 Issues

[cruiser54]

I have updated Post 2 in my tips to reflect the highlighted changes. 

 

Renix Jeep C101 Connector Refreshing

 

 

The C101 connector on 1987 and 1988 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and increased resistance over a period of almost 25 years. The C101 connector needs to be cleaned at least once in the lifetime of your vehicle. Chances are it’s never been done before.

 

Almost every critical signal between the engine sensors, injectors, ECU, and some to the TCU, travel this path through the C101 connector. 

 

That said, the cleaning described below is a real MUST DO right off the bat. But, I strongly advocate eliminating the C101 at some point by following the procedure with photos in Post 27. Soldering skills are required and it takes about an hour. 

 

The C101 connector is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the  ¼” bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time.

Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth.

 

If you have a small pick or dental tool, tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter before bolting both halves back together. 

 

 

Revised 05-03-2014

 

[Eagle]

Interestingly enough, although there was a TSB covering removal of the C101 connector that came out around 1989, whether or not it makes any difference is very much random.

 

I bought my 1988 XJ new in January 1988. Soon after I bought it, the dealership was sold. I didn't like the new ownership or the new service manager, so I tried another long-time Jeep dealer that was actually closer to home. On one trip in for something unrelated, the service manager told me about the TSB for the C101 and he strongly suggested that I have it done. He claimed it would make the engine start faster, give me better gas mileage, improve emissions, and cure "early morning drive-off stall."

 

So I had the work done. The shop charged me $500 for it ... and it made ZERO difference in how the vehicle ran. No difference whatsoever. When I later mentioned to the service manager that I was disappointed because I had not seen any of the improvements he predicted, he told me he never said that.

 

The same shop also charged me for an oxygen sensor replacement that was covered by a recall notice. It took me almost a year to get reimbursed for that. Needless to say, I stopped going to that dealership.

 

My '88 MJ still has the C101 and it runs just as well as the XJ.

[cruiser54]

Interestingly enough, although there was a TSB covering removal of the C101 connector that came out around 1989, whether or not it makes any difference is very much random.

 

I bought my 1988 XJ new in January 1988. Soon after I bought it, the dealership was sold. I didn't like the new ownership or the new service manager, so I tried another long-time Jeep dealer that was actually closer to home. On one trip in for something unrelated, the service manager told me about the TSB for the C101 and he strongly suggested that I have it done. He claimed it would make the engine start faster, give me better gas mileage, improve emissions, and cure "early morning drive-off stall."

 

So I had the work done. The shop charged me $500 for it ... and it made ZERO difference in how the vehicle ran. No difference whatsoever. When I later mentioned to the service manager that I was disappointed because I had not seen any of the improvements he predicted, he told me he never said that.

 

The same shop also charged me for an oxygen sensor replacement that was covered by a recall notice. It took me almost a year to get reimbursed for that. Needless to say, I stopped going to that dealership.

 

My '88 MJ still has the C101 and it runs just as well as the XJ.

You're very fortunate. I still have all the TSBs from that era and I've never seen a TSB on the elimination of the C101. 

 

There was a suggestion on cleaning it though and I'm not sure that was published or just a good idea passed around.

 

I have witnessed the loss of signal, especially ground through the C101.

 

My experience on numerous of my family and friends Jeeps, along with the results posted up by others on forums who have done the cleaning/elimination has been totally different. I was able to do before and after readings on sensors with my DRB and see the difference in readings, O2 sensor activity, driveability, starting, and cold running.

 

If you are suggesting that this procedure is some kind of Hocus Pocus and are discouraging others from undertaking it based on your limited experience with it, you are doing them a disservice. 

[91Pioneer]

For the amount of time it would take to clean the C101 and tweak the terminals, it wouldn't take much longer to solder and permanently fix it. I haven't done either, but it's on my "to-do" list, the soldering. I actually like soldering :)

[cruiser54]

For the amount of time it would take to clean the C101 and tweak the terminals, it wouldn't take much longer to solder and permanently fix it. I haven't done either, but it's on my "to-do" list, the soldering. I actually like soldering :)

True story. Thanks for bringing that up. 

[onlyinajeep726]

I did it on my XJ and the occasional "early morning stall" has stopped so far.

[cruiser54]

I did it on my XJ and the occasional "early morning stall" has stopped so far.

Interesting. I'm not surprised given the issues I've observed over the years. 

[Eagle]

If you are suggesting that this procedure is some kind of Hocus Pocus and are discouraging others from undertaking it based on your limited experience with it, you are doing them a disservice.

I am suggesting that it might solve some problems if you are having problems, but it won't accomplish anything if you aren't having problems. My own experience clearly demonstrates the wisdom of the adage, "If it ain't broke, don't fix it."

 

I don't see how my experience in any way makes me "fortunate." I wasted $500 on being conned into having the shop perform a "fix" that didn't fix anything. How is that fortunate?

[cruiser54]

You're fortunate that you've had no KNOWN issues with your existing C101. 

 

Sure the con job isn't tainting your view of this effective and many times necessary repair? 

 

And maybe that I was a Service Manager at a dealership for 12 years?

 

I NEVER did the kind of stuff that some putz did to you.

[onlyinajeep726]

I think, at a minimum, we can all agree that eliminating it certainly will not hurt anything.  That, in conjunction with the sensor ground update and tweaking sensors to give the ECU correct parameters, will not make anything worse.

[AeroNautical]

To go from this:

 

 

To this:

 

 

Is worth it alone, in my opinion. Cleans it up nicely. 

[cruiser54]

I think, at a minimum, we can all agree that eliminating it certainly will not hurt anything.  That, in conjunction with the sensor ground update and tweaking sensors to give the ECU correct parameters, will not make anything worse.

I KNOW it helps. I've SEEN it help. I've MONITORED the results. The sensor ground upgrade is actually part of the C101 elimination. How can anyone go wrong? 

[Eagle]

To go from this:

 

 

 

To this:

 

 

 

Is worth it alone, in my opinion. Cleans it up nicely.

This is a VERY unfair comparison, because the first photo does not show an undisturbed C101. It shows a rat's nest of loose wires after someone has ripped them out of the C101.

[AeroNautical]

 

To go from this:

 

 

 

To this:

 

 

 

Is worth it alone, in my opinion. Cleans it up nicely.

This is a VERY unfair comparison, because the first photo does not show an undisturbed C101. It shows a rat's nest of loose wires after someone has ripped them out of the C101.

 

Cmon man, it wasn't meant to be a fair comparison. People who have a c101 know what it looks like undisturbed, I just wanted to be a bit more dramatic with the comparison shots.

[onlyinajeep726]

Not to get off topic, but PFC, I see you have the dual diaphragm XJ booster and the later model steel valve cover.  Now time for the open style cooling conversion lol.

[cruiser54]

 

To go from this:

 

 

 

To this:

 

 

 

Is worth it alone, in my opinion. Cleans it up nicely.

This is a VERY unfair comparison, because the first photo does not show an undisturbed C101. It shows a rat's nest of loose wires after someone has ripped them out of the C101.

 

Actually, what's very unfair is for you to Pooh-pooh the C101 elimination because you got hosed in the late 1980s. Evidence has shown, and supported  the C101 elimination. 

 

I think you need to get over being butt-hurt over 25 years ago and snap back into reality based on emperical evidence to support the facts here. 

[Eagle]

I think you need to get over being butt-hurt over 25 years ago and snap back into reality based on emperical evidence to support the facts here.

I have a ton of empirical evidence. I have one 1988 XJ that had the C101 removed and spliced. I have one 1987 XJ that still has the C101, a 1987 MJ that still has the C101, and two 1988 MJs that still have the C101. The 1988 XJ that had it replaced doesn't run any better than the four that still have it. That's empirical evidence.

 

I have no problem with anyone cutting out the C101 if they have the time and inclination to do so. If there are electrical issues that affect circuits running through the C101 it's an obvious place to check. I just don't see it as being a necessary item of work for people who aren't having problems.

[cruiser54]

I never said it was. You just haven't seen what I've seen. 

 

 I have evidence by using the factory scanner that although the vehicle seems to run just fine, the C101 is altering the signals to and from the ECU. The Renix system is adaptable enough to still run "good". A simple tap on the C101, or gentle wiggling of the wires surrounding it, not unlike hitting a bump in the road, will most always change a reading. Most all very important engine management signals and grounds go through that crappy connector. And I live in Arizona!! No rust, moisture, corrosion.... What about the guys in the rust belt, South, near the ocean? Only gonna be worse. 

 

A perfect example of this is the 87 I just did the elimination on. 

 

I was ready to condemn the slowly responding O2 sensor but decided to wait until the C101 elimination was done. After it was done, the O2 sensor was switching like it was new. 

 

And, the guy who owns the Jeep said it has never run this good before. 

 

I've seen the same with IAT, CTS, MAP and TPS readings. 

 

Hopefully we'll get some responses back to this thread from those who perform the procedure. 

[64 Cheyenne]

Regardless, a chain is only as strong as its weakest link, IMO, eliminate the C101.

BTW its on my to do list for the 88, eliminate, not just clean.

[AeroNautical]

Not to get off topic, but PFC, I see you have the dual diaphragm XJ booster and the later model steel valve cover.  Now time for the open style cooling conversion lol.

Eh, never fix what isn't broken. My old booster was just about shot, and I got the newer valve cover when the lines to my stock renix one broke, and I didn't realize at the time they sold entire vacuum harness kits for it. My cooling system works like a champ. Sitting in traffic in the dead of summer near or at 100 degrees, all I have to do is flip my secondary fan on and my temp doesn't hardly approach 200. Heat blasts hot, too. I was gifted with an MJ that the PO took care of in regards to the cooling system. 

[onlyinajeep726]

Very good!

[metrictonner]

Every electrical connection problem; which means sensor problems, electrical device problems (fuel pump, fuel injectors, dash upshift lights etc), ignition problems, were traced to the c201, c202 connector female contacts opening up.  I figured this out after listening to everyone's grounding, connection cleaning, c101, and new parts recommendations for my problems and getting absolutely NOWHERE.  After 25 years that tight U-turn that the wiring harnesses makes at the ECU opens up just about every female contact with the added bonus of now there is room for corrosion and dirt to add to make an intermittant open connection perminent.  Tight contacts neither get corroded or dirty at point of contact.  Clean all you want but if the male and female contacts in the connectors aren't mechanically rubbing against each other you have an open circuit.  It may wiggle around awhile and give you an intermittant problem and maybe even appear to dissapear for a while with a new connector on a new part but 25 years of wear and tear on the connectors will show up eventually as an open circuit.

 

Dielectric grease just jams itself into the opening and INSULATES folks, just like corrosion and dirt IT MAKES AN OPEN CIRCUIT PERMINENTLY OPEN.  No matter what that idiot on AutoWeek told you: THROW AWAY YOUR DIELECTRIC GREASE.

 

Same thing with the vacuum connections.  After 25 years they open up too.  But in this case, the plastic fittings, hoses, elbows all need to be sealed with RTV. 

[onlyinajeep726]

Where is the C201 and C202 connectors and what are they for?

[onlyinajeep726]

Meant to ask you Cruiser... is there any potential MPG gains by doing the elimination and ground update?

[neohic]

I've been meaning to do this on my '88 as well. What I really don't like about it is that you're left with that giant loop of wire loom:

 

Image Not Found

 

Personally, I think there's already too much loom that traces all over the place. It's just ugly. Anything special to look for if removing the C101 and cutting the wires way short so it doesn't have the loop?