Question about Toyota 4Runner

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It appears just lately that I have a short in my electrical system. Left sitting for a day or two the battery loses it's charge. Jumping and driving for a brief distance the battery becomes charged and all is well. This has happened just in the last week or so. I have an aftermarket alarm system but it has never caused problems before. How do I go about locating the problem. Thanks for any advice. Mark

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Please see my tip at . These are generic instructions. If you get stuck or need specific instructions for your car, please get back to me with model, year and engine info.

Posted on Oct 02, 2010

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  • pmbrick Oct 02, 2010


    Thanks for the reply, you got me on the right track.........but will take you up on that PHASE II offer. First: !998 Toyoto 4 Runner : V6 : 4wd
    1: Checked battery w/engine off....12.4 volts w/engine ON......14 volts......seems O.K.
    2. Set multitester on disconnected positive battery cable, connected negative battery post
    3. Showed draw of 1. volts that slowly goes down to around .04
    4. Pulled underhood fuses one at a time
    5. Only fuse to allow the meter to drop to 0 after removal was a 15 amp for DOME (which also controls clock, radio and door locks)
    Now hear is what is confusing. With the 15 amp fuse installed and when the rear hatch door is open or closed and the three way switch for the rear dome light is in the OFF and/or DOOR position the meter still shows a variable .150 to .04 voltage draw but in the ON position drops to .000
    6. Now after reinstalling the positive cable the drivers door lock button will lock the doors but not unlock. The passenger side works fine. It also seems that the override safety button does not function.
    7. I do have an aftermarket alarm system that seems to work fine (horn honks with 15amp fuse out, locks don't respond but that seems correct with the fuse out.
    8. Read somewhere about possible faulty switch in the rear hatch door lock???
    9. I'm not familiar with all the relays, ect. in this 4runner but I wonder if that is the next step.
    I'm really, really amazed at the bells and whistles Toyoto has come up with, like the headaches I went thru trying to troubleshoot the factory trailer plug......after much internet searching I discovered the FAULTY little black box and replaced it with a junkyard $10.00 replacement. The task was so much easier with good people like yourself giving a helping hand.
    Thanks in advance for any suggestions,


  • Jeff Turcotte
    Jeff Turcotte Oct 03, 2010

    These designs give me a headache. Unfortunately I do not have a full set of wiring diagrams. Good job isolating to the DOME circuit. That DOME fuse runs to the DRL module but not the door locks. It isn't clear without seeing the circuit that what you have observed is a short at the rear dome light. That said, and since you have a meter, it might be worth your time to open that light and interrogate the wiring. It should have one hot lead, one grounded lead, and one lead that should ground when a door is opened. I would focus on that last one, which could be getting a signal from the DRL module, which I am guessing gets inputs from all of the door switches and integrates them to all of the dome lights. If that wire is always ground, even when all doors are closed, you have a bad switch somewhere. You could further troubleshoot to the particular door if you had the diagram for the module. Look for the module in the engine compartment relay box. Maybe it will have a diagram on it (NOT). If you aren't lucky, at least you could plug the module in and out with the doors closed to see if it's clicking (when it shouldn't be). If it clicks, I'd say there is a short or bad door switch making it click. If it doesn't click, maybe the short is in the module (or maybe it's solid state and never clicks?)! You could carefully break open the module to see if anything is burned up or out of order inside. No harm done if you need a new one anyway, but don't tear it up in case it is good.
    Sorry, this is about all I can tell you without more of the diagrams.

  • pmbrick Oct 03, 2010

    Thanks.......I'm off to search for that DRL mod. and bang the heck out of it........well, maybe just gently check it out.........It's times like this I wish I had my 1963 Dodge truck back. Ha!!



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