Backup light strangeness

Discussion in 'Other Manufacturers' started by hobbit, Apr 20, 2010.

  1. hobbit

    hobbit He who posts articles

    Has anyone seen a situation where the white reverse lights, particularly
    on pickup trucks, come on when either a remote-clicker is used
    to lock or unlock, or even if a door is opened, or maybe the
    interior light is turned on? I'm *not* talking about the high-mount
    clearance light that includes white lights into the bed, I'm
    talking about the backup lights on the tail. If you're familiar
    with a vehicle whose stock wiring system tends to light those
    at times when it *isn't* in reverse, what type of vehicle is
    it and what, if you can find out, is said about this in the
    owner's manual?
    My own wiring mods don't count, and this in fact is part of some
    research into formalizing that stuff.
  2. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    Not sure if this helps, but my cars (GM midsizers) have what they call "perimeter lighting" where the key fob unlock event switches on the tail and reverse lights, along with the front parking and headlights, for about 15 seconds. Your description above resembles this behavior. This feature can be enabled or disabled along with other BCM options.

    I have a Haynes manual for the car, and the wiring diagram shows the following:
    -Left and right backup lamps connect to the backup lamp relay in the rear fuse block with lt green wires.
    -The relay is hot through a 10 amp "backup lamps fuse".
    -The relay is activated through the wire connected to the BCM. Since the relay shows the coil connected to 12v on one side and the BCM on the other, it appears the BCM lights the reverse lights by grounding the light blue wire.

    The parking lamp circuit works the same way, with the tail lights and license lights connected on a common circuit with brown wires, and the Park Lamp Relay is energized via the white wire going to the BCM.

    There's no way to know if the GM trucks share the same wiring method, but I know that they do have the same "perimeter lighting" feature. I am not sure GM is sensible enough to say "brown wire is always tail lamp circuit". But I know that some local auto parts stores have a display of Haynes manuals, and they have wiring diagrams in the back. A casual glance and a good long term memory are all that's needed to visualize the lighting circuits.
  3. hobbit

    hobbit He who posts articles

    I think that's what I've been seeing. What year of vehicle?
    It seems to be newer ones. And I will say that when I've seen
    it it's often been in circumstances that confused the crap out
    of me, like someone walking up to such a vehicle parked head-in
    while I'm coming along and I think some clown is about to back
    out at me. Whoever came up with this needs to be smacked over
    the head with the FMVSS, even though 49 CFR 571 standard 108
    doesn't actually say anything specific about this.
  4. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    The Haynes manual I have is for 2004-2007 Chevy Malibu, but the wiring would be the same for any GM Epsilon car (Saturn Aura, Pontiac G6), and there is no reason to doubt that the wiring would be similar for the newer midsizers and the compacts as well.

    I can confirm your experience of thinking that a car with the reverse lights is about to run you over. On plenty of occasions, I have seen people react to the backup lights when these cars get "booped". Other cars will beep or people will stop before walking behind the car. This perimeter lighting seems to be the factory default setting, and I never disabled it because I tend to do more driving at night, and I use the light around the car to check for obstructions before driving away. One interesting and boneheaded fault in this "feature" is that remote starting the car turns on the parking lights, and then when you unlock the door, the reverse lights go on. So people who are parked behind you think the car is running and in reverse with no driver, and they have a mini panic attack thinking they are going to need a new grille.
  5. seftonm

    seftonm Veteran Staff Member

    I have seen this on a number of newer GM cars, vans, and SUVs. I hate it, and can't believe somebody decided it would be a good feature to add. Way too much potential to cause confusion in parking lots.
  6. hobbit

    hobbit He who posts articles

    So the prevalence of the "feature" probably means it's not
    specifically illegal to implement or use. Good, it's already
    become part of a writeup that I hope to finish tomorrow...

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