So I have a few faults I think are all related and I'm trying to locate the source. I have to following fault codes:

Body Control
B1C57-14 (2F) Passive start ignition relay coil circuit - General electrical failure - circuit short to ground or open
Engine
P0504-64 (2A) Brake switch A/B correlation - Algorithm based failure - signal plausibility failure
Transfer Case
U0122-87 (2F) Lost communication with vehicle dynamics control module - Bus signal/message failure - missing a message
Transmission
P0500-00 (2F) Vehicle speed sensor A
U0416-86 (2F) Invalid data received from vehicle dynamics control module - Bus signal/message failure - signal is invalid

I started looking at the Brake switch A/B correlation issue since it seemed the easiest to resolve. I already tried replacing the brake pedal switch. It didn't fix the issue. From the iiD tool, the live values shows that the "brake pedal lamp switch" toggles on with the pedal being depressed and off when released, but the "brake pedal brake switch" remains on constantly with or without the pedal being depressed. Are these two switches in the brake pedal switch? There are 4 wires running to it so I'm going to assume so. Base on the wiring diagram, it appears one switch defaults to being open and the other defaults to be closed. I assume the opposite occurs when depressing the brake pedal.

It appears the Green / Purple wire feeds power to the brake lamps, but also to the BLS port of the ABS module and back to the CJB / Hill descent Relay. I assume this side of the switch is the "brake pedal lamp switch" and since the brake lamps are not illuminating constantly but do illuminate when pressing the brake pedal that this portion of the circuit is working correctly.

That leaves the Purple / Green wire that goes from the brake switch to the BS port of the ABS module. There is a junction (C2411-3 C2412-3) somewhere, but otherwise this wire does not branch anywhere, and goes to the ABS module only. Unless this wire is somehow shorted with a hot wire or the switch is defective, I don't see how it can hot be all the time. I'll test the new and old brake switch with a voltmeter to make sure it's not it. I watched Christian's video about the "complexity" of the switch so I'll make sure it's in it's functional mode before testing. If the replacement switch is defective, this would be the ideal scenario as it's an easy fix. If that all checks out then, I will test the Purple / Green wire to ground (with the switch disconnected) to see if there is voltage. It should be 0. If its not, it will appear the wire is shorted to hot somewhere. I don't know where this junction (C2411-3 C2412-3) is. I will have to find it and investigate. I already disconnected, inspected and electrical contact cleaned the connection to the ABS sensor. I suppose the short could be coming from the internal portion of the ABS module. If all my diagnostic tests check out okay, I guess it could just be the ABS module telling the ECU that switch circuit is on even if its not. I hear these are problematic and may require replacing. I hope mine is good.


Of a side note, sort of. The live readings for the yaw rate sensor is very erratic. It goes back and forth from 0 to XXXXXX (some very high number, I'm not sure of the units or if its just some numerical value that has a very high range). It fluctuates very quickly and this is when the truck is parked, motionless, engine off, key position 2. I'm not getting a Yaw rate sensor circuit error code on the iiD. Since I was concerned there could be water damage in the center console, I took out the console and I now have the yaw rate sensor accessed. I don't see any sign of water ingress. I have the battery disconnected as I don't want to trigger the airbags, if that's possible. I think the yaw rate sensor is fine, but is there a way to test it while I have access to it? Some of the tests I want to perform require hookup the battery back up so I want to button center console back up. Does anyone know if this yaw rate sensor needs to be replaced based on this behavior or is it just due to the ABS module? The yaw sensor also plugs solely into the ABS module. Well there is a connector (C2245-4 C2243-4) that I will need to inspect as well, where ever it is. Does anyone know where that is?

Thank you!

 

I just went through this hell a few weeks back. https://landroverforums.com/forum/lr...d-line-126339/

For me, it was 3 issues acting together: 1. the brake switch which was new failed really soon after install. Buy an OEM one. 2. I had corrosion on the transfer case control module (easy to get at but you have to pull the battery), and 3. and this one is 95% of the causes out there: along the floor on the US right front passenger side door sill right before it goes UP the A pillar, there's a 3-way splice of a thin red wire held together with blue tape. Mine corroded and was completely disconnected. This is most people's issue it seems.

If you find a 5-way red splice without power, that's not it, it's the 3-way.

I might have pictures and can look tonight.

Another cause could be water in the central junction box but now you're into "graduate level studies" as access is a PITA and I would do all 3 above first before you try for the CJB.

Again I will look for pictures. - scooter

 

Ok here's the splice. Not the best picture but this was one of my 'Eureka' moments, when I found the right wire it just slid right out of the splice, had completely separated. You can see the start of the bend up to the A pillar of the chassis. Again this is US passenger side.

BTW, I had vehicle dynamics errors too and those completely dropped away once I had resolved the P0504 error. I think the P0504 triggers the vehicle dynamics errors downstream.

In terms of order of checking, I would 1. replace the brake switch (5 minute job), 2. find and if needed fix the splice (reconnect the 3 wires if needed), and only then look at the transfer case module. If those are all ok, then you're probably going to be forced to inspect and if needed clean corrosion off the CJB and if you have to do that let us know because I have suggestions to make it go easier. I got really good at pulling the CJB and reattaching it and there is a technique that helps. Ok, splice pic is here:

 

Thank you for your response. I'm exciting to go investigate this. It just so happens that I have all that wiring accessible now. I'm also troubleshooting issues with the wireless key fob not working so I've been tracking down the three way splice of the green wires in that area, lol. Unfortunately those splices look somewhat okay. I tested for continuity across them. I might solder them just to make sure. To be honest I haven't yet checked to see if the fob is even programmed correctly. The key does start the car, so I assume it is, but I don't know. I ordered and finally have an iiD tool from Lucky8 (that came with an extra key). I'm planning on going to a locksmith today to have it cut, then I'll go through the procedure of programming / reprogramming all the keys.

I regress. So I already pulled out the CJB and I replaced the rubber grommet behind it for the sunroof drain tube more than a month ago. The grommet was rotten and the tube was draining inside. Though this car has been kept relatively dry (either garaged or covered with a tarp). Though there definitely has been water in there. I inspected the CJB for corrosion. I did find some on the upper most pins and cleaned them up. I did not open the CJB. If the three red wires aren't an issue, do you recommend I do that? Are you aware of any post where someone has done that?

That upper area where the CJB, connectors, etc. are, is really clean and dry. Its down by the floor board, in the channel with the wiring loom, that is pretty disgusting. All the wrap was rotten. I don't know if it the residual adhesive from the wrap or if someone rubbed dielectric grease everywhere. Its all very gooey. I kind of feel the goo has added insulative properties, but I don't know what it is. Probably someone spill something in there. I guess it all has to be cleaned up. Any recommendation for that? A big bottle of purple power, scrub brush and a shop vac is what I'm thinking. I don't want to introduce more water to the area, but I'll get it all clean and dry before reinstalling the battery.

I already replaced the brake switch and I've pulled both the TCCM and ECU from behind the battery, inspected for corrosion, cleaned and reinstalled. I'm running out of straws here, but I'm hopeful that everything is stemming from the wiring in the passenger's side floor board. I will get to work and report back.

 

Well you were spot on regarding this. I found the 3 red wires and there were completely corroded through. And apparently I didn't search very well for the green wires earlier because I found them right away today. Same thing, corroded straight through.




Thanks a lot! I was able to cleared some codes today, and I can lock my vehicle with the remote key fob now

I still have the following fault codes. I'm going to dig around in that same area for more corroded wires. It seems there are a lot of splices put together with only electrical tape.

Body Control

• B1C57-14 (2F) Passive start ignition relay coil circuit - General electrical failure - circuit short to ground or open

Parking Aid

• B1B52-96 (2F) Rear sounder - Component failure - internal failure

Transfer Case

• U0122-87 (2F) Lost communication with vehicle dynamics control module - Bus signal/message failure - missing a message

Transmission

• P0501-00 (2F) Vehicle speed sensor A range/performance

The speedometer isn't working and I know it worked for a moment in time. I assume this is related to the transmission fault and because of the behavior (sometimes working, sometimes not) I sense another wiring issue. You don't perhaps know what wire I should be looking for now, do you?

 

So I'm looking further up the floor board near the A-pillar and I think I see a few more splices (blue electrical tape). Since I'm in here, I'm just going to solder all these splices. I can't seem to get to these though. The carpeting is glued to foam and appears to be glued to the floor. I've managed to pry up a little, but I still don't have access. What would help more would be to remove the plastic shroud / mounting bracket for a few harnesses and grounds. Does that come out relatively easy? As long as I take a few pictures beforehand I'm sure I can put it back in correctly. It's just a matter if that comes out or not.

 

Soldering the red wires resolved the following codes:
P0504-64 (2A) Brake switch A/B correlation - Algorithm based failure - signal plausibility failure -Resolved
U0416-86 (2F) Invalid data received from vehicle dynamics control module - Bus signal/message failure - signal is invalid -Resolved
I ordered a new parking assist rear sounder and installed it, so that fault code is resolved as well.

These are the last fault codes I'm getting:Body Control
B1C57-14 (2F) Passive start ignition relay coil circuit - General electrical failure - circuit short to ground or open

Transfer Case
U0122-87 (2F) Lost communication with vehicle dynamics control module - Bus signal/message failure - missing a message

Transmission
P0500-00 (2F) Vehicle speed sensor A
I recalled getting this Vehicle speed sensor A error when I first bought the truck. Along with it, I was getting a fault of the front right wheel speed sensor. Also of note, the speedometer did not work. I replaced the front right wheel speed sensor, both codes went away and the speedometer started working again. We'll the VSS A code is back, the speedometer doesn't work again but I'm not getting the front right wheel speed sensor fault. Hmm... Due to just replacing the wheel speed sensor, it being the problem again was low on the list of differential diagnoses. Well perhaps it is. Not discussed in this thread, but in my other thread where I was trying to troubleshoot issues converting back to air suspension, I put these aftermarket air struts on the truck which resulted in the front end collapsing onto the bump stops and the tire rubbing hard against the fender wells. I had tried installing these air struts between replacing the wheel speed sensor and switching back to the coil struts. Well, I decided to take a look and took the front right tire off again. I also wanted to get to the ground point in the wheel well to make sure it wasn't causing issues. Apparently when the truck was resting on the bump stops, the wheel speed sensor wire was getting cut between the fender well and the upper control arm. The prior owner first tried putting these air struts on the vehicle (failed by not first addressing the other fault codes on the vehicle BTW) and apparently cut that wheel speed sensor too. So perhaps everyone should be aware that there could be a pinch point that can cut your wheel speed sensor wire when you suspension bottoms out. Or perhaps only if you put cheap aftermarket air struts on your truck.



I ordered another new wheel speed sensor. I don't know if I can run it under the upper control arm or not. I don't know if I need to since I don't plan to use those air struts unless I find some strut extenders for them (they're too short in the front). I'm not sure if the wheel speed sensor is going to clear all my remaining faults, but I hope so. I'll tell you after I replace it and see what the iiD tool says.

Thanks everyone for the help.