2016 Prius Touring - Blind Spot Monitor Error

Discussion in 'Gen 4 Prius Main Forum' started by Sung Woo, May 14, 2021.

  1. Sung Woo

    Sung Woo Junior Member

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    Four Touring
    This is totally on me for not noticing when I bought the used car, but I just realized my 2016 Prius Touring's "BSM" indicator wasn't on. I turned it on and it says there's a malfunction. Is there no way of diagnosing this except to take it to the dealer? Reading Edmund's experience with this (The Blind Spot Monitor Saga - 2016 Toyota Prius Long-Term Road Test) makes me think this is gonna cost a pretty penny if I were to get it fixed. Any chance of a DIY solution?
     
  2. Elektroingenieur

    Elektroingenieur Senior Member

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    If the “Blind Spot Monitor System Malfunction Visit Your Dealer” message is appearing, the reason has almost certainly been stored in one of the blind spot monitor sensors, which are also the computers that control the BSM system, as a diagnostic trouble code (DTC) or as an entry in the BSM abnormality history.

    To retrieve this information, you’ll need a Toyota Techstream diagnostic system or equivalent, discussed at length in other PriusChat threads. Inexpensive OBD II scan tools made for engine and emissions diagnosis wouldn’t be able to communicate with the BSM sensors, which Toyota designates as “Master” or “LH” on the left side and “Slave” or “RH” on the right side.

    Once you know why the message is appearing, turn to the Repair Manual (more info) for troubleshooting procedures. A loose connector or wiring problem might be easy to fix yourself—but to replace a BSM sensor or do the beam axis confirmation procedure, you’d need special service tools, Reflector C (09870-60040) and the Base Stand (09870-60010), which may be too costly to buy for one-time use.

    The BSM sensors, part number 88162-0W270 (wrongly described on parts.toyota.com as a “Liftgate Object Sensor”) for either the left or right side, have a list price of $865.56 each, but I wouldn’t buy one until you know that the problem isn’t just in the wiring to the side mirrors or buzzer, for example.
     
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  3. Sung Woo

    Sung Woo Junior Member

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    Thanks so much for this info. Just ordered the mini VCI cable from Amazon and found the software online, so I'll give this a go.
     
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  4. AzWxGuy

    AzWxGuy Weather Guy

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    Wow, really ? $865.56 each ?? Those will be the next parts that are shamelessly pilfered from our vehicles.:(

    EDIT: Ah, the rear left and right side radar detectors. Looked it up in my owners manual. I thought we were talking about the parking assist sensors. I'll bet they are a pretty penny also.
     
    #4 AzWxGuy, May 15, 2021
    Last edited: May 15, 2021
  5. Sung Woo

    Sung Woo Junior Member

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    Four Touring
    So I hooked up the cable and fired up Techstream, though now that I took pictures of the sensors, I feel kinda stupid. Because it's pretty obvious.

    The error code is C1AC2, and it's a misalignment issue:

    https://www.tochr.net/520/slave_module_horizontal_axis_misalignment_c1ac2_.html

    It's the slave module. And comparing it to the master, the problem is pretty clear. Some kind of a physical damage took place to whack it out of alignment. It looks like the inner ring is gone, and there are some scuffs/marks that probably also looks like it points to damage.

    Is it worth it for me to take the bumper off to see what's what? Is it also possible for me to reset the error code to see if it happens again? Or is this one of those things that can't be reset? I pressed the button to reset the previous DTC codes, but this one would not go away.
     

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  6. kevinwhite

    kevinwhite Active Member

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    I had a similar problem.

    I didn't see a low concrete bollard in a parking lot and sideswiped the side of the car where the right-hand sensor is located.

    The bodywork didn't look significantly damaged, just scraped a bit, as the panel just sprang back into place. However, a few weeks later I started getting a similar error message about the BMS.

    I took it to the dealer and they gave a similar response about misalignment. After repairing the bodywork they attempted to recalibrate the radar without success and eventually had to replace it for about $1,000 (plus body shop repairs).

    Overall a rather expensive loss of attention for a couple of seconds.

    kevin
     
  7. Elektroingenieur

    Elektroingenieur Senior Member

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    Yes. The round objects seen in your photos are ultrasonic sensors for the intelligent clearance sonar system. As seen in Google Image Search results, the blind spot monitor sensors, which use 24 GHz radar, are rectangular units, normally hidden by the bumper cover.
    If you’ve tried clearing the DTCs, but the DTC returns immediately, then the problem most likely still exists, and you’ll need to follow the troubleshooting procedure in the Repair Manual.
     
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