Factory FOB works, interior switches do not

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by subgyro, Apr 19, 2014.

  1. subgyro

    subgyro Member

    My '99 Bourbon K2500 SLT with barn doors recently developed a wee bug... None of the three interior door lock switches (third at the very rear) will lock or unlock the doors. The factory FOB will lock and unlock the doors without fail, so I'm thinking it's not the relay.....?

    Every other switch seems to work fine, power windows, power mirrors, although I've never been able to adjust the passenger mirror. Does this raise alarms to start checking out the wires going to the passenger door? Could some short be happening in there that blocks out the interior switches but not the FOB?

    I have browsed through 8 pages of posts regarding door lock issues and the only ones seeming close to my issue involve after-market alarms or remote starters, but my Bourbon is blissfully un-molested. (So far. There will be one hell of a stereo upgrade very soon. It floors me that the factory stereo can make FM sound like AM.)

    Thanks in advance for any suggestions!
  2. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    I think you may be on the right track when you consider looking at the door wiring. I would start with the driver's door, only because it is opened more than any other. Look for a broken wire in the bundle that passes from the door to the truck body.

    I wish I could offer the wire colour to look for.
  3. Caddiac

    Caddiac Epic Member 5+ Years 1000 Posts

    X2 on the wire as the culprit. I don't know if there were significant differences between the two vehicles but I have the manuals for a 98 K1500. If I see something interesting I will post back on this thread.
  4. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    If you could provide the LOCK/UNLOCK wire colours, it would help
  5. Caddiac

    Caddiac Epic Member 5+ Years 1000 Posts

    You say you have never been able to adjust passenger side mirror. Is that in both directions ( up or down, left or right)? How about the heater for the mirror, does it work? I am looking over the schematics (assuming they are basically the same 98 to 99) and reviewing the diagnostic procedures. You would think that it would be a key indicator of where to look when the FOB works but none of the three switches will. Too bad the guys that published the factory manual don't think like that.....

    I am reading the circuit operational description and wonder if there is a common issue between the mirrors and the door locks. Does not appear to be .......yet.....

    - - - Updated - - -

    The orange wire feeds all the door lock switches. The gray wire runs to the door lock motor from the door relay. So if a test lamp is handy, check one of the door switches to ground. That will at least tell us what end of the circuit might be causing the problem.

    The schematic is located out in two different sections of the manual; the keyless entry section and the door section. The relationship of the connections on the diagram suggest that the door relay might be bypassed by the FOB receiver circuit.

    Good thing I am bald; no hair to pull out......
  6. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Actually, when you think about it, the passenger mirror is adjusted from the driver's door panel, so I would suspect a problem in the driver door wiring.

    Ground is common, it is usually a black wire.

    The other thing that is common, is the arm rest switch panel. I have had rain destroy a panel. If the window was doun in a rain storm, or the door left open for a period of time, rain will short out the control panel. I have had printed circuit run burn out. If you find this is the problem, soldiering a piece of wire across the burned area will work.
  7. Caddiac

    Caddiac Epic Member 5+ Years 1000 Posts

    Both the FOB circuit and the switch circuit are before the relay. Again, assuming the wiring between the two model years is the same, then the problem is not going to be found in the doors but most likely under the dash. The "convenience center" is located under the dash left of the steering column. Check all the connections there and see if that does any thing.
  8. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Exactly, the fob operates the relay and the locks work, therefore the relay is good and the circuits after the relay are fine. The door switches should operate the relay as well, that is the circuit that needs to be checked.

    A common failure is a broken wire where the door opens and closes at the hinge pint. The constant flexing breaks the wires without breaking the insulation.
  9. subgyro

    subgyro Member

    It's kinda fun watching you two go back and forth, talking out the problem!

    The passenger mirror has never worked in the 5+ years I've owned the truck, up or down or left or right or heater. Back when the electrochromy-magic-tinting mirrors did work, nothing happened over there either, but I'm not sure that one was ever supposed to dim.

    Weather is nice enough up here now that I'm bombing around in the car, so will get to checking out the wires in the next week or so.

    Thank you, Caddiac and RayVoy, for your help so far!
  10. subgyro

    subgyro Member

    Question, is this the mythical Convenience Centre? The place where I ripped out the oh-so-irritating buzzer?


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