BSMUnavailible issue

A couple of months ago I pushed in the corner of my rear bumper while backing up a trailer. I drove with it that way for a week before I disassembled it and banged it back into shape. There was no damage to the wiring, and the Ultrasonic unit was not touched. I did have to pull off one back-up sensor to remove the bumper cover but it slid back in when I reassembled. For the last two months the BSM and RCTA have worked fine, but while driving last Friday I got the warnings that both were "UNAVAILIBLE". I talked to the dealer who was no help, they just want to throw parts at it and do a calibration with a total estimated cost of $1500.

Does anyone know what the most likely failure is? Does the back up sensor I moved have anything to do with this? The sensors for the 2021 have the same parts number as those for 2020 which are much cheaper. Are they the same? Is it the ultrasonic unit? Is their a way to test it?

I don't want to be like the dealer throwing parts at this. I could replace all the sensors, both Ultrasonic units and wiring harness for under $500, but that is a lot of effort if someone has a simple solution. I appreciate any help that can be given

 

Separate subsystems, the ultrasonic parking sensors and the BSM don't "talk" to each other. BSM is standalone.

The BSM sensor has to be calibrated to a zero point and has a small tolerance. You can try an auto collision place, they may come in cheaper. Replace the bumper parts yourself and have them run the calibration.

Calibration procedures are up on the TIS site; you'll need specialized equipment.

 

I have a 2016 that has been through similar (bumper hits that were relatively minor) situations. I have had frequent similar issues with the BSM and parking sensors going offline as unavailable.
Same with the dealer offering to (recalibrate) my sensors with no guarantee for a lot of money. On the parking sensors I first replaced a damaged harness and a couple of sensors with aftermarket clones. These have worked fine.
The BSM system can work flawlessly for months then cycle through a period of unavailable alarms. On both systems, I simply shut them off and wait a while and restart. This has always worked.
I have attempted to track for patterns and and this is what I have come up with and do: Check the connections-however, ones connected and the harness secured, I have never had issues with any connection failure beyond a visibly damaged rear harness. Second, I am sure that ice, road dirt, or anything remotely impeding the parking sensors will set off the alarm, etc. with the BSM, I sort of-kind of suspect that it’s more likely to go offline when the bumper caps are dirty, but not always… it’s just that things seem to go better after I detail the exterior. (The BSM sensors are outrageously expensive. Dealer quotes me around $800 for the part three years ago-when the visibly damaged harness was the issue)
What has worked each snd every time for me, knock on wood, is to simply shut the switch, let it sit for a while, repeat until it resets (check for obvious obstruction when convenient).
I love the sensors and would replace components if needed, but frankly, Living with the quirk is like a marriage. LOL in the end she comes through for me!

 

I find the BSM and the RTCA to be indispensable. With the truck sitting so high it is easy to loose sight of smaller vehicles in traffic. The light on the mirror has saved me from changing lanes on top of some small car that just wants to ride in my blind spot.

For the rear sensors the 2021 and 2020 and older have the same part number but cost significantly different. Can the 2020 sensors be used in the 2021?

 

Ditto on that! The truck is high and huge. I love my sensors and would repair or replace them if needed. I have a tricky driveway with sidewalk, trees, stop sign, etc. kids, dogs, joggers, (Ugh) in the city and always back into it for the added safety.
It would be great if the module could be removed and bench tested somewhere instead of buying one without knowing if it’s defective. Is not your newer truck still under warranty?
The fact that both systems went out simultaneously, points to an electrical/power condition similar to what mine was like when I bought the truck used. (Had a similar right rear bumper cracked corner from the prior owners argument with a snowbank) Both systems did not work. When I located the wiring issues it was in the rear harness that feeds both sensors. It runs across the rear bumper and captures both the parking and BSM modules. This harness connected to a feeder that runs forward. At the time I had the dealer print out the diagram and got the part number that way. I think the harness was under $100. As it turns out, my year had a recall on the rear bumper corners (hard plastic) so I asked them to replace the harness I had bought myself and they did the recall. BSM worked and parking sensor had a bad connection so that sounded the unavailable alarm. I just went ahead and replaced it myself and that worked out fine.