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2007 Toyota Prius - C1554

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by AmericanIdiot, Jun 8, 2018.

  1. AmericanIdiot

    AmericanIdiot Junior Member

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    So I started my 2007 Toyota Prius today and the dreaded triangle of death showed up along with the MFD displaying "P/S". I hooked up my OBDLink LX to it and read the codes off of the EMPS ECU. It came back with C1554 - EMPS relay circuit malfunction.


    It looks like the only resolution to this is to replace the ECU. I can order a used one online and have it show up in about a week. In the meantime, would I be doing any long term damage by driving it with manual steering?


    Thanks!
     
    #1 AmericanIdiot, Jun 8, 2018
  2. dolj

    dolj Senior Member

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    Well, not quite. If the relays have failed, then yes you would be replacing the ECU as the relays are built into the ECU. However, the inspection procedure does get you to check the fuse, two harness circuits and the connectors before concluding the relays are toast.

    DESCRIPTION

    When a problem occurs in the system, the power source relay (built into the power steering ECU) circuit and the motor relay (built into the power steering ECU) circuit are shut off to stop power assist. It is necessary to replace the ECU when there is a problem in the relay because each relay is built into the ECU.

    Detection Condition/Trouble Area:

    DTC No. DTC Detection Condition Trouble Area
    1 C1554 Power source relay malfunction
    • EPS H-fuse
    • PIG power source circuit
    • Power steering ECU


    I have attached the inspection procedure.
     

    Attached Files:

    #2 dolj, Jun 8, 2018
    SFO and Raytheeagle like this.
  3. AmericanIdiot

    AmericanIdiot Junior Member

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    Thanks for the diagnostic page. Would it be ok to drive without power steering? Or would that cause some damage?
     
    #3 AmericanIdiot, Jun 8, 2018
  4. Gorhamax

    Gorhamax Junior Member

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    Not sure if driving without power steering would cause damage, although I doubt it.

    However, in many cases when a relay fails a good tap can cause it to click closed. The ECU is located behind/above the steering wheel in the dash. I’m assuming you’ve already replaced the ECU, but if not smacking the dash behind the steering wheel could get you by temporarily.
     
    #4 Gorhamax, Jul 2, 2018
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