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Gen2 - Tail light /brake out

Thread in 'Lights / Lighting' started by gavin T, Nov 7, 2019.

  1. gavin T

    gavin T Member 2nd Gen Owner 4 Wheel Drive V8 Engine

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    RR tail light is out(purple/orange wire). FR hyper blinks. turn truck on - no outage light, pres brake or hazards or right turn signal get the outage message. i believe the SJB checks resistance in the line. then displays error message, but does it stop sending power to the circuit if it senses the issue?

    replaced bulb - RR still out.
    checked fuse - 10amp fuse does all brakes and etc
    switched the bulb with its outlet to RL - it works on the RL but RR still out.
    i also popped the positive terminal off for 20 minutes and reattached - RR still out.
    checked for power with multi-meter getting power to the RR running light but nothing to the RR brake/turn light. so i know the ground (black/yellow) is good.
    so it appears to be the purple/orange positive wire is having a ground issue. this happened intermittently now its full time.

    can someone tell me how i can track down the grounding issue(harness connections) or is there a way to check the SJB for a issue? although i dont think there is an issue with the SJB because the fuse would prevent that and the SJB would throw the check RR signal error immediately.

    i didnt check for power at the trailer harness connector ( anyone have diagram of connector assuming its also not a purple-orange wire)
    i know this purple-orange wire is in the wiring harness in the driver rocker/kick panel area. as i believe the SJB is right there behind the internal fuse box, i guess i could check capacitance from that area to the RR bulb socket and that will tell me if its between the two.
     
  2. Todd Z

    Todd Z Well-Known Member 2nd Gen Owner V6 Engine V8 Engine

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    I have seen the front bulb failing cause this too....
     
  3. gavin T

    gavin T Member 2nd Gen Owner 4 Wheel Drive V8 Engine

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    spent about 3 hours yesterday. checking grounds again, fuses, trailer harness. and swapping bulbs. couldn't find a wiring diagram anywhere online god knows why this is such a common vehicle ford must have cracked down hard.

    Thanks for the input Todd, always appreciate your help on the forum. i haven't checked that yet... that would be awesome. i also haven't tried plugging in my trailer to the 4-Pin Tow harness. i thought the front turn signals use an entirely different wire and relay inside the SJB? either way going to check that bulb even though its working.

    update:
    Multi-meter Testing showed very low power going to the right signal/brake wire (purple/orange) i am guessing the SJB sends a test voltage to check line resistance- basically the CANBUS does a test for bulb then displays the check RR bulb message and then changes

    with the turn signals off- i checked both signal wires. orange-purple for RR and grey-purple for RL. Both have .080V but when the left gets power its alternating 0-6-16 volt ( guessing the multi-meter cant keep up with rapid changes.
    right when it should be getting power gets .6V alternating to 0V.

    i opened the wiring bundle at driver door and found the purple-orange wire and tested for power there no different than the RR socket/harness.. and that's only 1ft or so before it runs into the SJB. i checked capacitance on the wire starting at drive door to the rear right signal at the harness and that was good. i did not however send 12V from the driver door area to the bulb b/c i didn't want it to back feed to the SJB. i didn't know if there was a diode in there, and did not want to cut the wire. and have to re solder as it was dark out at 5pm.

    if i have to get another SJB this POS is getting SOLD- manifold leak and all.
     
  4. Todd Z

    Todd Z Well-Known Member 2nd Gen Owner V6 Engine V8 Engine

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    That sucks... keep us posted... these stupid electronic things are annoying... Does the light work though?
     
  5. gavin T

    gavin T Member 2nd Gen Owner 4 Wheel Drive V8 Engine

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    i haven't not gotten the light to work. it started intermittent. if you turned the car off and on it would work again( no warning no hyper blink. went on for 2 weeks or so - then the light went off for good and message is permanent. been like this for 2 weeks now. ford is SCUM for putting non crucial relays in a sealed all in one box. if you look up the sjb its basically a fuse box but sealed with resin. there is NO reason i should have to replace a $500 part because one blinker relay blew. like are you kidding... Nissan Frontier in my soon future.
     
  6. Todd Z

    Todd Z Well-Known Member 2nd Gen Owner V6 Engine V8 Engine

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    it does sound like that stupid SJB.... that sucks.... of course bypassing may be a pain.... All manufacturers are using boxes and things like this for crap... Every manufacturer has its issues....
     
  7. gavin T

    gavin T Member 2nd Gen Owner 4 Wheel Drive V8 Engine

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    hooked up my trailer with 4-pin harness..... brake lights and turn signal worked on the trailer! i was so happy plus its pitch black at 6pm and about 20degrees out here in PA.. i didn't even notice if the taillight on the truck came on or not... i need to find a wiring schematic for the turn signals. i am assuming --the turn signal/brake wires (purple/orange and grey/purple) are spliced to the white green brown yellow wires for the 4 pin harness.
    any idea where i can find that schematic?
     
  8. Todd Z

    Todd Z Well-Known Member 2nd Gen Owner V6 Engine V8 Engine

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    Can you Jump the dam bulb off the trailer pin ?? LOL that pin is direct from the switch and I believe it doesn't go through the SJB....
    I have the 2010 schematic book at home and may be able to take pics.... you can buy the book or if some one has the CD on ebay or here can post..... I hope this isn't from the accident??? could be....
     
  9. gavin T

    gavin T Member 2nd Gen Owner 4 Wheel Drive V8 Engine

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    i saw a 2010 wiring diagram for the trailer harness on explorerforums and it had the trailer wiring going all the way to the SJB. which then makes me think why is that the case and not just spliced in at the end... because it would be way cheaper that way and simpler...

    sjb wiring to rear turn signal diagram would be SUPER appreciated!

    [​IMG][​IMG][​IMG][​IMG]
     
    Last edited: Nov 14, 2019

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