2022 Pro, Interior Lights Stay On; BCM Replacement?

I've done my troubleshooting and I think I have narrowed it down to the BCM, or "Multiplex Network Body ECU Computer Assembly" part 89220-04C90. But, I wanted to just run my steps over you folks before I order this $400 part (then $XXX for programming).

Issue: interior overhead console lights and rear dome light remain on, regardless of switch position, truck on/off, in gear, etc. I have verified all door switches function, as intended. The only way to get the lights "OFF" was pulling the 7.5-amp fuse. So, with the 3-position light switch (overhead console) in the "OFF" position, when I insert the fuse back, I hear a relay click in the BCM - this tells me the fault is within the BCM itself. Based on the wiring schematics, it looks like the BCM can turn the lights on regardless of the 3-position light switch.

Dealership was useless. They charged $160 to "swap a console out, replace broken clips, other BS". Spoiler alert, they didn't replace the broken clips, nor did they fix the issue.

As an additional note, I took apart the overhead console, no issues. Disassembling the existing overhead console required busting the polymer welds. I verified the switch was functioning, as intended with a meter; no traces found damaged on the control board.

I ordered a replacement, installed the replacement overhead console, same issue.

Truck is a 2022 pro with 75,000 miles. Bought new on May 3, 2022 with 3 miles on it.

A few codes are present. I do have an OTT tune, codes may be from that. Tune was done at around 40k miles. I do not have a timestamp on the codes. Relevant codes:

• U0140 Lost communication with body control module
• U0142 Lost communication with body control module "B"

So, I think at this point the BCM is to blame. Has anyone replaced one? I guess it isn't wise to try to open the BCM up, see where/what the fault is. I assumed I would need to order the BCM and have the dealership install/program, I don't think I have that ability.

 

Why are you doing any of this? You're under warranty, right?

 

Warranty ran out at 36,000 miles. My truck has 75,000 miles.

 

My sincere apologies for missing that part. WOW you drive a LOT!!!!!!!!!

 

IF switch doesn't do its job I don't see how the BCM would.
Switch selects ground i.e. ILE (PWM), OFF, ON (straight to ground).

 

That’s not the same diagram from the third gen service manual. See the picture I posted. The switch is on the negative side of the circuit; a fault with the BCM would still complete the circuit regardless of the switch.
And, I replaced the entire overhead console, yet the problem persisted.

 

Since you are a "selective" reader, good luck to ya.

 

And you physically ohm'ed out and troubleshot all 4 door sensors as well as the bcm door input leads?

You're one of the first with this issue, meaning you can throw everything you want at it, but my gut says it's not the bcm. Or it is the bcm, but was caused by an alteration to the truck.

 

Do you have a full system bi-directional scan tool?

If so are you able to look at the data for the Main Body ECU and see what the input's and outputs show?

There's also bi-directional controls for the interior lights you could try to see if it has the ability to turn them on and off.

 

I did not ohm the door sensors. However, there are no other signs of a door issue.
I don’t disagree; I can only assume that something with the tune caused this. However, I got the tune in 2022 so it is still strange to have put 50k miles on the truck then this problem arises.

I can’t see any more data than the code itself. I can do a full scan, but that’s all. What do you mean by bi-directional? To clarify, the lights remained on regardless of any switch in the truck, engine, or other condition.

 

I think what @caribe makaira posted is the inner circuit for the upper console.

Your scanner can't view data from the Main Body ECU?

Bi-directional means the scanner has the ability to send commands to a module and view data at the same time, it's useful to see if the module has the ability to control things as well as to run various tests on certain systems that wouldn't be possible to do without it.

 

I’ll have to look into how to send commands. The scanner is a 5610 which says it has that ability. I’ve not done that myself before. Thanks

 

5610 what brand?

 

Innova. I’ll update it in the morning and see what commands it can do.

 

This makes more sense, thank you.

edit: a few things:
I think the three position switch overhead can be ruled out. My steps:

1. Removed existing overhead console assembly
2. Bust welds, disassembled. Inspected, switch tested, no issues.
   
3. Replaced entire overhead console anyway; problem persisted.

According to that diagram, I’m interested in that “DOME CUT” relay, and that “No. 1 Room Light Assembly”; I need to find those.

 

No.1 Room Light Assembly is the cabin lamp (not map lamps).
Dome cut relay is inside the Driver's side junction box (part that the Main Body ECU attaches to).
Cut off relay provides fused power for 20 min after engine off. In case any/all cabin lamps are left ON. Timer resets if any door opened among other variables.

 

Have you tested if you left the map lights ON (by pushing them individually to turn off)?

 

Yes, tested in multiple conditions - problem persists.

Thanks for the diagrams - where are you getting these? I could not find anything like this. I think I need to be checking the dome cut relay and the cabin lamp switch - when I look at the schematic you posted, it looks like the overhead console lights can get their ground connection from the cabin lamp switch, does that sound correct?

 

Yes, they do.