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Discussion Starter · #1 ·
So for the last six months every time the rear underside of my JKU got wet, I'd get the "Service TPM System" message, a flashing error light that turned solid after two minutes, and dashes for all of the tire pressures.

Everything would be fine once it dried out - it would show the correct pressure in all four tires. Splash the underbody with water or spray thru the rear wheel wells when washing it and it would throw the error again.

There is a TPMS receiver module mounted on a bracket above a rear cross member that is responsible for collecting the signal of the two rear tires. It looks like a pretty flimsy little plastic box with an upper and lower half that snap together, making for pretty easy water infiltration. I removed it today, put some dielectric grease on the connector, and plugged it back in.

Now it doesn't work at all - constant error light and dashes for each tire.

I tried to source the part number on the module and had no luck at all. Then I tried sourcing the part number on the bracket the module is attached to and was able to find the bracket and the module together as one unit for less than $30. The part number is 68214825AC

It should be in next week, I'll post back if that fixes things (I sure hope so) but I'm also wondering if the new module needs to be ID'd or paired to the existing system?
 
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Mine does this every couple weeks. on off. I'll be interested to see if this is the actual culprit but sounds like you're on the right track. Keep us informed.
stealership has been blaming mine on lift kit and bigger tires but mine didn't start throwing this until 42k miles and now has 55k
 

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Discussion Starter · #4 ·
Mine does this every couple weeks. on off. I'll be interested to see if this is the actual culprit but sounds like you're on the right track. Keep us informed.
stealership has been blaming mine on lift kit and bigger tires but mine didn't start throwing this until 42k miles and now has 55k
Mine is still under 3yr/36k warranty but I was skeptical the dealer would say the same thing - that the fault was due to a leveling kit and/or aftermarket rims and tires even though the factory TPMS sensors were re-used. I figured for less than $30 I could avoid having to take it in and potentially be without it for several days.

Then again, I could always replicate the failure by spraying the rear under body with water. We'll see what happens when I change out that receiver module.
 

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Discussion Starter · #5 ·
Well I finally got the new module in and had a chance to change it out yesterday.

Didn't make any difference. I still get a "Service TPM System" error on startup and "-" for all wheels.

At this point I suspect it's the actual connector that plugs into the module (remember this issue started when the rear under body would get wet) but it's on a very short pigtail and part of a larger harness so it's not something I can replace myself.

Time to leave it at the stealership for a week or more..........
 
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"you're killing me smalls"

I've been waiting on pins and needles, just knew that module would do it.
Let me know how it turns out as mine is still in the same place as yours.
 
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you both must have something that can reprogram the jeep for the bigger tire size correct?

i disabled the tpms on my jeep with the flashpaq since i run lower pressure in my 37's than the stock tires. but then again, i dont have the evic screen either, just a light that is annoying when the system says a tire is low.
 

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you both must have something that can reprogram the jeep for the bigger tire size correct?

i disabled the tpms on my jeep with the flashpaq since i run lower pressure in my 37's than the stock tires. but then again, i dont have the evic screen either, just a light that is annoying when the system says a tire is low.
I'm running 35's, bought it new and did lift, tires everything with <2,000mi and have superchips flashpac. Have it set to i think -0-, worked great until 42,000mi
then the light come on and check tpms. Sometimes goes off for a week or so then right back on. The only difference in mine is that it shows the air pressure for each tire even with the light on.
 

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Discussion Starter · #9 ·
you both must have something that can reprogram the jeep for the bigger tire size correct?
Yup. Not sure if reprogramming the ECM for a bigger tire size has anything to do with TPMS but even when I had TPMS disabled it doesn't inhibit system error messages.

The error message is "Service TPM System" which means the computer found some sort of fault with the system itself, regardless of whether it's been disabled or not.

I restored TPMS function when I switched back to a set of wheels that have the OEM sensors in them. It was working fine for months.

In my case, I know it's related to something under the chassis getting wet. Whenever I would wash it or got thru a car wash that has the under-body wash or even just drive in the rain, I'd get the error and it would go away in a day or two when whatever was affected dried out.

Since I isolated it to the rear TPMS receiver module mounted on the crossbar, I replaced that module but suspect it has to be ID'd to the vehicle. So I removed it today and put the original one back in. The TPMS worked for about 5 minutes, showing the correct tire pressure for all four tires, but then faulted again with a beep, the flashing TPMS indicator that turns solid after two minutes (indicating a fault with the system, not the wheel sensors) and the EVIC displays the error "Service TPM System".

Which is why I suspect that connector is bad. Will find out in a couple of weeks when I'm able to leave it at the stealership. At least they have the diagnostic equipment to figure it out.
 
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Given most connectors these days are sealed, your connector should be sealed as well. So there should be small seals pressed in on the wire end side and there should be a large seal sealing the mating ends of the connector.

How do the terminals inside look?
Any sign of oxidation or dirt?
 

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Discussion Starter · #11 ·
Given most connectors these days are sealed, your connector should be sealed as well. So there should be small seals pressed in on the wire end side and there should be a large seal sealing the mating ends of the connector.

How do the terminals inside look?
Any sign of oxidation or dirt?
And therein lies the problem. It really is a bad design, I suppose they felt it was protected being mounted above the cross member.

This particular connector is a 4 pin phenolic that has minimal moisture sealing. Can't see the internal pins on the female end because they are tiny and there isn't much play in the harness to work with; the male pins on the receiver module are fine.

I couldn't even get a small prick probe into the four female pins so I could measure front-to-back continuity with a VOM. The wires themselves exit the plastic loom and enter the female connector with no moisture seal. When both halves are connected it's pretty tight but the back of the female portion is open to the elements.

This is a miniature version of the electrical connector on the driver side frame rail of the Ram 1500's that causes problems ("Service Electronic Throttle") when it gets wet. Same issue.......
 

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Wow. That is interesting.

Can you tell what gauge is the wire?
(sorry I'm still in the waiting room for our Wrangler, but I'm seasoned DIY mechanic)

If the wire is not too thin, the connector might be changed to a sealed type connector, like e.g. Metripack 150.

I also wonder why the issue is not more wide spread. Do lot of people delete the TMPS system?
 

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Discussion Starter · #14 ·
Wow. That is interesting.

Can you tell what gauge is the wire?
(sorry I'm still in the waiting room for our Wrangler, but I'm seasoned DIY mechanic)

If the wire is not too thin, the connector might be changed to a sealed type connector, like e.g. Metripack 150.

I also wonder why the issue is not more wide spread. Do lot of people delete the TMPS system?
It's pretty stiff, I want to say it's solid versus stranded. And small - probably no more than 22 gauge.

While you can reprogram the TPMS system with new values or even disable it, you can't turn off fault detection.

I agree it seems like it would be more widespread. Maybe I "discovered" this weakness because I make a habit of pressure washing the under body. Unless you were routinely and completely submerging the rear axle to the point water was over the cross member the most moisture this mounting location might see is fine road mist.

Then again, I could be completely wrong and there's nothing wrong with the connector and my making it fail by getting that area wet was just a coincidence. I don't think so but we'll find out for sure when the stealership gets a shot at it.
 

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Discussion Starter · #15 ·
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There is a TPMS receiver module mounted on a bracket above a rear cross member that is responsible for collecting the signal of the two rear tires. It looks like a pretty flimsy little plastic box with an upper and lower half that snap together, making for pretty easy water infiltration.
I started looking for a picture of the receiver on the internet, just to see the connector. The receiver sure looks like something that was designed to be mounted away from the elements.

Can you include a picture of how it is currently installed.

With a broader search, I found a similar issue. Receiver is mounted more or less exposed.
http://www.m3post.com/forums/showthread.php?t=904325
Also, they are referring to the receiver as 'antenna' and it seems that in this (BMW) instance the replacement needed re-progamming.
 

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Discussion Starter · #17 ·
I started looking for a picture of the receiver on the internet, just to see the connector. The receiver sure looks like something that was designed to be mounted away from the elements.

Can you include a picture of how it is currently installed.

With a broader search, I found a similar issue. Receiver is mounted more or less exposed.
Does the TPMS RDC antenna need recoding upon replacement?
Also, they are referring to the receiver as 'antenna' and it seems that in this (BMW) instance the replacement needed re-progamming.
For some reason when you try to source the P/N on the module itself, nothing comes up even in the Mopar system. But when you search for the part number of the bracket, that is easily sourced and it includes the receiver module. Here's an example:

MODULE. Tire Pressure Monitoring. Part Number: 68214825AC | eBay

The bracket wraps around the center of the rear cross member, with the receiver sitting on top.

I suspected the WCM would need to be reprogrammed when a new receiver module is installed, thus the immediate failure when I swapped in the new one. When I put the original back in, it worked for about 5 minutes before throwing errors again. I'm still convinced it's that crappy connector, I'll try to take some pics of it and the actual module today.
 
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Discussion Starter · #18 ·
Here's where the rear TPMS receiver module is mounted:
 

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Discussion Starter · #19 ·
Here's what the assembly looks like when it's unbolted from the cross member:
 

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Discussion Starter · #20 ·
Unplugged, here's what the mating portion of the female connector from the wiring harness looks like:
 

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