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Locking doors blows fuse

Discussion in 'Gen 2 Prius Technical Discussion' started by ORPrius, Nov 20, 2022.

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  1. ORPrius

    ORPrius New Member

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    Hello! I have a 2008 Prius that blows the 25amp #11 fuse every time I lock the doors. I have read through the previous posts but am hoping with a more specific description and actions someone might have an insight.
    The fuse blows when locking by using the switch on the inside of the drivers' door, by using the key fob and by using the mechanical key. It does not blow when unlocking by any method. I have removed all door panels and unplugged all electrical components inside the doors (except mirrors and speakers) hoping it might be an actuator but when I sit in the car with the key and lock it with the fob, it still blows the fuse. I think my only option now is wire tracing which seems overwhelming with the sheer number of wiring components and tight spaces. I was hoping someone might have experience or an educated guess or point out something I've missed to narrow down the possibilities. Thank you!
     
  2. ORPrius

    ORPrius New Member

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    Additionally: Since posting I also used a meter from the line side of fuse #11 to ground and I get 12v. I also did a ground check with an ohm meter from the load side of fuse #11 to ground then kept checking while plugging in each connector one by one. There was no evidence of a short to ground (but maybe other components in the wiring system interfere with that test method).
     
  3. bisco

    bisco cookie crumbler

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    idk, but locking with the mechanical key makes me wonder. it only affects the drivers door. could a wire be pinched in the process?
    or, i wonder if mechanical locking sends power somewhere like the door switch.
    try disconnecting the driver door actuator, and locking all the doors
     
  4. ORPrius

    ORPrius New Member

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    Normally, locking the driver's door with a key initiates electronic locking of all the doors, however, with no fuse/blown fuse it just locks the driver's door old school. I did fob lock and key lock with ALL door wire connections unplugged and it still blew the fuse making me think the problem is between the fuse and the mechanism that receives the fob signal and/or the exterior lock which, when it has electricity, initiates the same process.
     
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  5. bisco

    bisco cookie crumbler

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    maybe corrosion at the sks ecu? hopefully, someone will have a better answer for you
     
  6. vvillovv

    vvillovv Senior Member

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    does the fuse blow when locking the passenger side door and or while sitting in the passenger seat and using the fob to lock? back doors and seats?
     
  7. mr_guy_mann

    mr_guy_mann Senior Member

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    If it blows the fuse when you trigger a "lock" function, then something on the ACT+ circuit (yellow wire) is shorted to ground. That's the circuit going to all the door actuators, and it's switched briefly to 12V+ to power to lock motors in the "lock" direction. The ACT- circuit (green wire) is held to ground at the same time.

    The polarity is reversed for "unlock". Your fault (almost) has to be in the wiring (ACT+) between the BCM and whatever you unplugged. Go look at the wiring diagrams for details.

    If there is any kind of aftermarket alarm system in the car- remove it and repair any hacked wiring from where it was installed.

    Posted via the PriusChat mobile app.
     
  8. ORPrius

    ORPrius New Member

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    Thank you for your specific directions. There are no aftermarket products. If I have disconnected all the fittings at foot level on each side (photo) so that there is no longer a connection to the wiring going through the doors and along the floor, and the fuse still blows instantly when locking with the fob, wouldn't that indicate that the problem is between either of the connector groupings at foot level and the fuse box or maybe the fusebox itself? As for the wire tracing, I'm working on it...
     

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  9. ChapmanF

    ChapmanF Senior Member

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    Have you looked at the wiring diagrams yet?

    You know what Westheimer said ... a coupla months in the laboratory can save you a coupla hours in the library.
     
  10. ORPrius

    ORPrius New Member

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    I'm looking at the 2006 manual which apparently is valid for my 2008. I must be reading it wrong or maybe it isn't valid for '08. Pic 1 shows a yellow wire from 1H on the Body ECU (Pic 2) to the connection at the floor IE2 (where's the fuse in this schematic?). The 25 amp fuse in #11 for door locks is at the bottom of the Body ECU. It's pulled - no fuse in #11- and I still get 12v at the IE2 pin where the yellow line comes in to the connector 1.png 2.png
     
  11. ChapmanF

    ChapmanF Senior Member

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    It's on the previous page, supplying the ALTB terminal of the body ECU.

    You say you're seeing 12 V at IE2 pin 9 with the fuse out? When? When attempting a door lock operation, or constantly?

    That does seem odd. Has every downstream connection where ACT+ appears been disconnected?

    I wonder if the fuse would continue to blow with ACT+, ACT−, and ACTD all disconnected at the junction block. That might suggest a fault in the body ECU itself.

    It is able to switch each of those three lines to either the +12 or the ground rail. Relays aren't mentioned in the circuit as far as I can see, so pairs of semiconductors may be doing that. If one in a pair has failed in a conducting state, and then the other is triggered to conduct, that could blow a fuse all right.
     
  12. mr_guy_mann

    mr_guy_mann Senior Member

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    That would be extremely odd, as the diagnostics for the lock actuators say that +12V is applied to terminal 4 (which is ACT+) in the "lock condition".

    I wonder if that 12V is a bias from the BCM. Might want to measure voltage on ACT+ and ACT- with the actuators connected.

    Posted via the PriusChat mobile app.
     
  13. vvillovv

    vvillovv Senior Member

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    Have you checked the driver door main panel? It caught my eye when you mentioned you didn't discoonect the driver door mirror connector.
    Isolating these multi switched 2 3 and 4 way circuits can be frustrating for sure.
     
  14. ORPrius

    ORPrius New Member

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    In response to your questions, the arrow points to the hot wire (hot on the male side) and it is constant. All connectors at both kickplates are disconnected):
    hot wire.png

    That said, I needed to travel for work and my kid needed her car the next day so I sent it to mechanic filling them in on all that had been done so far. The mechanic focused on the fuse box and said they "found a wire at the fuse box shorting out against the frame". I asked for specifics (which wire? which part of the ECU?) but couldn't get any. Sorry I'm traveling and can't complete this post with a more definitive answer for others that have a similar problem but it is solved. Thank you all for your insight and suggestions!
     
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