Multiple problems after o2 sensor short to ground

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Steve 72, Apr 2, 2026 at 7:59 AM.

  1. Steve 72

    Steve 72 Junior Member

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    A wire melted on downstream o2 sensor causing short to ground. The efi fuse blew and replaced it. Now I am experiencing no power steering, no climate control no power windows no combination meter lights. I immediately replaced the capacitor that always goes bad and put back together. No changes. All fuses check out with multimeter. Replaced b and c integration relays in the fuse box under hood. No change. Suspect ecu at this point. Help needed thanks
     
    #1 Steve 72, Apr 2, 2026 at 7:59 AM
  2. saneesh8

    saneesh8 Member

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    Any codes?
     
    #2 saneesh8, Apr 2, 2026 at 9:39 AM
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  3. Steve 72

    Steve 72 Junior Member

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    ?
     
    #3 Steve 72, Apr 2, 2026 at 11:43 AM
  4. Steve 72

    Steve 72 Junior Member

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    C1242
     
    #4 Steve 72, Apr 2, 2026 at 11:43 AM
  5. saneesh8

    saneesh8 Member

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    #5 saneesh8, Apr 2, 2026 at 12:54 PM
  6. ChapmanF

    ChapmanF Senior Member

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    It helps to describe the tool you used to retrieve trouble codes, because not all of them can talk to all of the dozen or so ECUs in the car, so you sometimes see some of the trouble codes you have, but not all of them.

    C1242 is a code that comes from the brake/skid ECU. From the symptoms you describe, I suspect there are other ECUs in the car that will also have trouble codes for a scan tool that can talk to them.

    But you might get some useful information by following through on troubleshooting the C1242 code you know you have. It indicates power may not be reaching one of the IG2 or IG1 terminals of the brake/skid ECU, and if you end up confirming that with a meter, you'll be onto something.

    Here's the link to those troubleshooting steps, from the thread saneesh8 linked to: PDF

    Notice that the fortune cookie for C1242 is given as "IG2 POWER SOURCE CIRCUIT", but when you actually read the DTC Condition, C1242 can either mean IG2 has power when IG1 doesn't, or IG1 has power when IG2 doesn't. The "detailed code" 87 or 88 tells you which—if you've got a scan tool that shows you detail codes.
     
    #6 ChapmanF, Apr 2, 2026 at 1:05 PM
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