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Driver Seat Belt Light Flashing

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by sas0611, Sep 20, 2021.

  1. sas0611

    sas0611 Member

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    Today my wife started her 08' prius and the driver's seat belt light continued to flash even with her belt latched.

    Tonight I hooked up my laptop to the data port and looked for possible causes. There are no stored codes. The switch in the seat belt latch appears to be working correctly. The software reports when the buckle is engaged and when it comes out. The passenger seat weight sensors seem to be working fine - when I sit on the passenger seat i see values of upwards to 80 LBS is being reported.

    There is no weight being reported on the drivers side of the car. When I sit in that seat one of the sensors reports a negative value and the other stay constant at about 2 lbs. I would think that like the passenger side something would register when sitting in the driver seat since there is a set of sensors for drivers side of car. If there is no sensor in the drivers seat then this makes perfect sense that nothing is showing up.

    So my question is this - if the buckle is sensed when it is in the latch and if If there is a sensor and it is bad would this cause the car's electronics to disregard anything that is going on with the buckle/latch sensor since it thinks there is no driver sitting in the seat. Is there some connection between buckle/latch sensor and weight sensors on the drivers side.

    My wife will admit herself that she is a slob. There is a lot of things that find their way under the seat and behind it. It would not be far fetched to think that something dislodged a harness or broke a wire under her seat.

    Any thoughts would be greatly appreciated. Thanks in advance

    Steve
     
  2. ChapmanF

    ChapmanF Senior Member

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    I don't think the driver's seat has occupant classification sensors the way the passenger seat does. When the car is being driven it assumes it has a driver. So probably the buckle switch is where the action is going to be.
     
  3. mr_guy_mann

    mr_guy_mann Senior Member

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    I looked at a wiring diagram and it shows dual-stage airbags for the driver and passenger. It also showed a driver's seat position sensor (as well as the driver's buckle switch) in addition to a "occupation classification sensor- front LH". The SRS system uses data from the Occupation Classification System ecu and the seat sensor/ buckle switch to decide whether to fire one or both stages of the airbag. If you have driver's seat weight in data then I would assume it does have OCS (like the wiring diagram indicates), and it should show something when someone is sitting there. If it doesn't show weight, then I might expect the system to set codes. What are you using to scan the car?
     
  4. sas0611

    sas0611 Member

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    Thank you for that information. I'm using the techstre
    Thank you for checking into this for me. I am using VCI with Techstream. There are no codes being set. The values are weird for driver side ( one is negative lbs). I will try and post a picture of the data list from the OCS ECU. There were 4 sensor (2 for right side of car and 2 for left). Each of the four had data for both Voltage and for Weight. Can you tell from your information where that sensor/wiring would be located and if there is any part numbers for it. I'm hoping it is just a connector/harness issue.
     
  5. ChapmanF

    ChapmanF Senior Member

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    I think the seat position sensor is the only thing there related to the driver's seat.

    The names of the four OCS sensors could trick you, because sure enough, they are called front LH, front RH, rear LH, and rear RH, but those all refer to the four corners of the front passenger seat cushion.
     
    burrito likes this.
  6. mr_guy_mann

    mr_guy_mann Senior Member

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    Sneaky bastidges.
    So I was looking at the "right front" front LH OCS sensor.

    ocs data.jpg
    So here is a data list for the OCS with "normal" values. I'd imagine if something doesn't jive (such as registering weight - "not vacant" in the passenger seat- while the passenger buckle switch was "unset") then it would keep the dash light on.
    Posted via the PriusChat mobile app.
     
    #6 mr_guy_mann, Sep 21, 2021
    Last edited: Sep 21, 2021
  7. sas0611

    sas0611 Member

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    I would never have occurred to me that they were calling out the 4 corners of the passenger seat cushion....
    Thank you for enlightening me. Any suggestions regarding what's causing the buckle up light to keep flashing since it seems the that the Driver buckle switch is working perfectly - set condition reported when latched and unset condition when unlatched.
     
  8. ChapmanF

    ChapmanF Senior Member

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    Puzzling. Have you found anything useful in the related section of the repair manual?
     
  9. Big Nick

    Big Nick Junior Member

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    I have a 2007 Prius with this issue. Was this ever resolved? I see nothing that would cause the seat belt warning light to blink but it does with the belt is inserted. Techstream shoes all good…
     
  10. sas0611

    sas0611 Member

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    I never got this resolved. Light still blinks even though driver seat belt latched into buckle. Techstream properly recognizes that the belt is seated into the the latch and will show the buckle / latch as "SET" when inserted and then when unlatched it shows it as unset. No one except you and I have ever commented that they have the same issue. I'd be apt to change out the latch if it techstream showed it never being set but it consistently show no problem with regards to distinguishing between truly latched and unlatched.
     
  11. sas0611

    sas0611 Member

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    So this is a confusing thread. Without my reading the whole thread over, I started it because in my particular situation, I was concerned solely about the driver's side safety belt warning chiming and blinking when i had driver seat belt buckled as well as when unbuckled. As the thread evolved some of the data points that were only relevant to the passenger side seeped into the thread. Specifically, ther passenger side is the only seat that tests for presence of a human - which makes sense. That passenger seat cushion has 4 weight sensors inside. This was very intersesting but had any bearing on my problem.

    So if you are asking about the drivers side blinking and chime sounding, my prior post is all I can offer.

    I do not claim to be an expert and I do recommend you have your car evaluated by professionals. I have chosen to ignore the warning lights and chimes. I was satisfied that the driver seat belt electronics were functioning as designed and were not detecting a problem. This was based solely on the ECU correctly reporting a latched/set and unlatched/unset signal. I don't know if there are other data points or integrated systems that may or may not be monitored by techstream that could be tangentially related that may point to something dire or of concern.

    Without a lot of knowledge or due diligence, in my mind it was logical to conclude that I could ignore the warnings. I also figured at some point, when I took the car into the dealer I would ask them to look at it. But I never took the car back to the dealership for anything.
     
  12. Big Nick

    Big Nick Junior Member

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    I never like to ignore a warning light and even more so as this is my daughter,s car so I took a shot and I have resolved the issue.

    Like you, Techstream showes all working and no issues. The buckel shows latched and the seat positioner works as expected. Nothing shows that there is an issue except that the seatbelt warning light is on and will not turn off when you buckle in as a driver with no passenger present.

    I replaced the buckle and now all works correctly. Took about 30 minutes to do the replacement, very easy, 4 bolts and 4 connectors for the seat and 1 bolt for the buckle. Turns out the switch in the buckle is a computer chip so likely something more than just and on/off switch. No idea how to test it, I just replaced it and now no lights when buckled in. Working 100% as expected. Got a brand new buckle for abuot $60 and I feel much better now... Love that car!
     
  13. sas0611

    sas0611 Member

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    Good job and wise decision. Thank you for the update and for telling us about the solution that worked for you. Best -
    Steve
     
  14. mr_guy_mann

    mr_guy_mann Senior Member

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    Actually, I looked at the wiring diagram and was wondering about the buckle. The passenger side buckle shoes a switch with a capacitor, but the driver's side also has a zener diode.

    Not sure why it's there but maybe that diode is bad and affects what voltage the ecu "sees" .

    Posted via the PriusChat mobile app.