Toyota BSM problem

My BSM stopped working at about 45k miles

I get the "BSM not available" message when ever I try to turn it on.

Also get DTC code of C1AC2. Which I believe was the slave module that was reporting bad or at least bad "alignment" (calibration?).

I hoped it would magically clear up when the weather warmed up.... but no such luck

I understand that the modules are at the corners behind the rear bumper. My first question is does any one know which side is the slave and which side is the master? I don't want to dismantle anymore than necessary and I would like to check for debris around the sensor and signs of water intrusion.

Also any ideas how to DIY the calibration? The calibration is way too expensive to do at the dealer IMO especially if it will need to be done every year or two.

 

I am having the same problem and DTC code. It started in the middle of a 4 hour road trip in a crazy snow storm a month ago. I don't have a solution yet but will follow along with this thread, if you don't mind.

 

Recently just completed 4000 mile road trip. Half way through I got the same message. Still won’t work, have yet to take it to the dealer.

 

Mine started during heavy snow and ice a couple months ago. I plan to check for debris around sensor and see if water got inside. Then decide if its worth it to proceed further if that doesn't produce some answers.

 

I was driving in rain on the highway for 12-16 hours a day 3 days in a row. Half way through that trip is when it failed. Power washed truck twice and still won’t work.

 

Here is what is found so far- the master BSM sensor is on the left (drivers) side & slave is on the right side

I disassembled the rear "bumber" (just a bunch of plastic really....) It is tricky getting the pieces apart, the instruction in this forum helps a little and at least points you in the right direction. As a warning I would say there is a very real risk of breaking something doing this.

There are three parts to remove to get to the BSM sensors
Part 1- the center plastic bumper step cover, this is the step above the hitch & between the license plate lights and the 2 steps on either side
Part 2&3- the end caps that cover each BSM sensor

Here are the basic steps to remove the bumper step-
1. remove the trailer light connector, from behind release the clips and push out then release the connector this ones is fairly easy
2. remove the license plate lights, from behind use small screw driver to press the release while gently tugging the wire (the connector is smaller than it appears at first, use a head light so you can see and still have both hands
3. unplug the 2 parking sensors on the footstep piece-I think with patience these can be removed now, I didnt and ended up cracking one of the plastic round retainer pieces which holds the parking sensor in place) I though I could just unplug after releasing the center step piece but think now I should have unplugged firtst. From what I have read its 50/50 chance of breaking the retaining clip on removal. YOU CANT BUY JUST THE RETAINER CLIP!!

All three of the above take some patience

4. next remove the step piece- there are three plastic rivet-plug fasteners (not sure what to call these things toyota p/n

$7 90467-07215 Tundra Tacoma RAV4 Corolla 4Runner Camry C-HR

90467-07215 ) two on underside on either side of the hitch and one behind the license plate (which should be removed). I used 2 smaller screwdrivers to remove the rivet fasteners. Take it easy with these- don't just stick one screwdriver in and pry- work one screwdriver under, then another screwdriver on the opposite side, next work them a bit and you will find that you get each to go under a little better- now pry both our gently any it pops right out.

5. remove the center plastic bump step cover. This is a tricky part you will find about 6 clips on the under side which release this, part plus about 6 which you cannot release. First release the six clips you can get to. After coming to the conclusion that it was physically impossible to get to the remaining clips I gently pried and they all released and nothing broke... (I think I may have been better of just pulling hard to remove- see my video I plan to post later)

6. next removed the end cap- remove 3 rivet fasteners from the under side and 2 from the front side between end cap and rear quarter panel- 5 total
then press done/work loose the two clips on the top inside (right below where the right and left bumper steps were located), next there is still one more clip which you cannot release (at least I couldn't find away to get to it), it is right above the back up sensor. Pull endcap straight back until it releases (or breaks off)

So i finally got it apart and this is what I found on the Slave BSM:
BSM connector looks good, no corrosion of water inside. No huge debris around the sensor. The back side of the sensor had corrosion (it is aluminum?) I scrapped off all the corrosion using a flat piece of sheet metal not scratching or anything. The reinstalled and tried BSM a couple times still same issue or course... Next removed BSM again and opened the sensor up. It has a nice thick silicon seal around it. I saw no sign of water entry. No obviously burnt components on side of circuit board i could see. The PCB appears to be coated which is good for water I suppose but makes it harder to see the components for damage. I used a stereo microscope to look at the PCB and didnt see anything obviously damaged. Could not see how to remove the PCB to inspect the backside. The PCB appears to slide over a connector header and 2 single Ground?? or just "PCB holder" header pins. I checked all these for continuity between these connections and they appear good.

I made some crappy video to help show all this i will try to upload or link to them in another post. Sorry the camera is all over the place I didnt have anyone to assist me with the camera. Hopefully will help someone or me if I ever do it again.

Not sure I would do this again or recommend it to anyone. I didn't get anywhere so far... I may look under the left side end cap just because I'm so close to it anyway..

One last thing is that the parking sensors are almost impossible to remove without breaking the retainer clip. Of course you cannot buy just the retainer... On recommendation on this forum I ordered a Tundra sensor and clip off of Amazon for $20 (p/n 89341-0C010). Will post if it really fits- it looks like the correct retainer.

Soooo not too thrilled with what Ive done so far. Not sure what else to check while this is apart. The BSM sensor is not worth replacing IMO

Not impressed with Toyota design on this at all. This is a real pain to take apart. I could probably do slightly better on a second attempt now that I have seen how it all clips together, maybe. Hats off to anyone that can disassemble rear bumper without breaking something.

 

There is a really good YouTube video from Victory Bumper showing the removal of taco rear bumper

 

This is the TW post I used to get an idea how to disassemble the bumper: https://www.tacomaworld.com/threads...bsm-support-installation-instructions.464513/

 

Nice wish I saw this first. Totally explains how to access the end cap clips for removal. And how to pry off the step. It pulls off allot harder than it looked in this video though. I was surprised nothing broke when I did that step.

 

Bought my 2017 in August and the bsm gave the error message during the first winter maybe 2000 miles on it. Brought it in said I could wait for the fix. After a hour I was chauffeured home as the problem was gonna take a lot longer. Got it back working by the end of the day. Said it was a computer problem.

 

I agree. Really crappy design, especially considering this is an Off Road truck which is bound to get the bumper scraped up. Ford has a much better design where the BSM is implemented into the rear tail light.

Does the sonar still work?