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Srs Airbag Light : Code 51

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by GasDohctor, Dec 22, 2012.

  1. GasDohctor

    GasDohctor New Member

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    Hi Guys, first time poster here. I have a 2009 Toyota Prius. The airbag/srs light came on a couple weeks ago and would come and go. Eventually it came and did not go. This didnt really bother me as I dont drive it much anymore and I figured it would be gone by the next time I went to start it up. (I also heard about connections under the seat being loose and hoped that was the problem.) Well I was wrong. Today I noticed it was still there so I decided to start diagnosing. I jumped the connector as my obd2 scanner only reads regular and abs codes (not srs apparently). The only code that came up was 51. Which is the driver side squib circuit. Many say that code 51 usually just ends up being the spiral cable. I simply find this odd as every button on my steering wheels works. Cruise control works fine etc. Idk how only 1 or 2 wires get messed up in that thing and how they turn out to be the ones for the airbag but I suppose its possible.
    My next step is to take a continuity tester to the 2 plugs that connect to the airbag to see if they are getting power.
    Does anyone here have any experience with code 51? I hope someone can chime in and help me out here.
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. I suggest that you find repair manual info at techinfo.toyota.com which is a subscription website. That will provide you with comprehensive troubleshooting instructions and safety precautions to observe.
    2. Since a continuity tester is basically a very simple ohmmeter that provides voltage to the circuit under test, I hope you will not use it to test the airbag itself, as that may cause the airbag to fire and if your face is in the way that could spoil your day.
     
  3. GasDohctor

    GasDohctor New Member

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    I already found a nice repair manual online that I have been going by. And I didn't blow myself up when i removed the airbag so I believe I will be fine in the reassembly of the unit. The only things I plan on testing with my ohmeter are the driver side squib things, the instrument panel wire, and the spiral cable (if possible). And my planned fixes are either the spiral cable or instrument panel wire at the moment as all connections look good near the squibs inside the steering wheel. I'm not really worried about the airbag going out on me. (Even though it has in fact gone out since the light renders it useless). Definitely another issue.

    Any other advice is appreciated.
     
  4. nh7o

    nh7o Off grid since 1980

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    Maybe someone that knows the specific current levels that are required to fire an airbag can chime in here. I would think that the few mA that typical DVMs in continuity mode would not be enough to trigger the bag.
     
  5. GasDohctor

    GasDohctor New Member

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    Bag is disconnected though so it really doesnt matter except for the purpose of proving Patrick wrong.
     
  6. nh7o

    nh7o Off grid since 1980

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    I checked and the trigger current is 1-3 amps to ignite the initiator and generate the gas. A typical DMM will make only a few mA, so it should be safe to probe the bag itself.
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The OP's idea of a continuity tester may not be a digital multimeter. It might be a bulb powered by a 6V lantern battery, who knows. The battery certainly is capable of producing the needed current flow to fire the airbag.

    I don't see the point of "continuity testing" if you have access to a DMM with an ohmmeter function. If you have a DMM then you can measure resistance directly.

    I also don't see the point of testing the wiring harness connector that connects to the airbag "to see if they are getting power" since you wouldn't expect to find any voltage until the SRS system decides that it is time to actually trigger the airbag.

    It would make sense to use an ohmmeter to verify that the connections between the SRS ECU and the wiring harness connector leading to the airbag are sound. However the connector should be removed from the airbag first, thus removing any possibility of triggering the airbag.

    Obviously, to do that you would need access to the wiring diagram and pinouts of the SRS ECU, hence I suggested the OP obtain repair manual info at techinfo.
     
  8. nh7o

    nh7o Off grid since 1980

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    It depends on the meter. In probing a circuit, I often use the continuity mode and the audible beep function, so that I can keep my eyes on the probes. One of my meters has the beep in the resistance function, the other has it in the diode test/continuity mode. In either case, the current used is too small to matter.
     
  9. GasDohctor

    GasDohctor New Member

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    Thanks for the replies. I have a cen-tech digital clamp meter i bought from harbor freight. Super cheap and has not let me down. After a lot of testing it ended up just being the ground to the actual airbag. The car has a rebuilt title and was in a front end accident so you can imagine what the wiring looks like. So I was simply testing to make sure none of the wires accidentally got ripped etc. So after probing all the way to the instrument panel and seeing everything was fine I reassembled it all and noticed the horseshoe was very loose to the airbag. I clamped it slightly, screwed the airbag in, fired her up and no srs light. :)
     
    Dino33ca likes this.