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2009 (!) electronic brake warning light

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Brooklin Prius, May 2, 2017.

  1. Brooklin Prius

    Brooklin Prius New Member

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    Location:
    New England
    Vehicle:
    2009 Prius
    Model:
    II
    The orange (!) electronic brake warning light on our 2009 Prius started to come on intermittently and now come s on and stays on. I took the car to the dealer and they found the following DTC c1231 c1242 c1377. The 12v battery and the brake control power supply tested ok. Freeze frame data for abs dtc showed a low voltage 8-9v. They then cleared the codes and drove the car. The light did not come back on when thy test drove the car. No codes returned. After about 50mi the warning light did come back on. The next step according to the dealer is to pull the dash and test the skid control ecu. Has any one seen this combination of codes and what was the solution? I can get to the skid control ecu but how do I test it?
    Ps the car runs drives and stops normally

    thank you Keith
     
    #1 Brooklin Prius, May 2, 2017
  2. ChapmanF

    ChapmanF Senior Member

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    What does the repair manual say those codes mean? I confess I haven't memorized them, but it's usually pretty clear how to proceed after looking them up.

    -Chap
     
    #2 ChapmanF, May 2, 2017
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Two
    1. Check the ABS1 and ABS2 relays. "Check" means that you remove each relay, apply 12VDC to the coil terminals, and measure resistance across the switched terminals. If the resistance is more than 0.5 ohms after accounting for the test lead resistance, replace the relays.
    2. If the relays are found to be good, then you could test the integrity of the wiring harness per the Toyota repair manual, at techinfo.toyota.com
    3. If the wiring harness is found to be good, then I would suggest you identify the skid control ECU part number, and order a used unit with that part number from eBay. There is no field test for that ECU besides whole unit replacement.
     
    #3 Patrick Wong, May 3, 2017
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