Left side blind spot not working

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Mark222, Nov 1, 2025.

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  1. Mark222

    Mark222 Junior Member

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    Hi all, I recently purchased a 2020 Prius and noticed that (only) the left side blind spot monitor does not work, the passenger side works fine. The lamp in the driver mirror works because it lights up when the car is started, but it never lights up when there is a car coming up on the driver's side. There are no dash indicators of any problem, and a repair shop scanned all the systems and found no codes.

    Any idea how to narrow down where the problem might be?
     
    #1 Mark222, Nov 1, 2025
  2. AzWxGuy

    AzWxGuy Weather Guy

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    The blind spot monitor and rear cross-traffic alert systems make use of two radar units mounted just behind the rear wheels under the wraparound rear fender. The fact that the indicator LED's illuminate in each rear view mirror says the system is booting properly. There would be a message in the multi-information display if there was a general system fault. You might also notice that rear cross-traffic approaching from your left are not detected either. It sounds like the system has lost alignment on the left side, requiring a visit to your dealer for adjustment. There are 12 pages in my owners manual beginning on page 349 describing the function of the system and other causes of malfunction.
     
    #2 AzWxGuy, Nov 2, 2025
  3. Robert21PrimeLTD

    Robert21PrimeLTD Member

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    FYI, first the Blind Spot Monitor (BSM) must be set to on. Also, see the attached list of when the BSM will not function. Your problem MAY to one of those listed. Good luck.
     

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    #3 Robert21PrimeLTD, Nov 3, 2025 at 2:24 PM
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