Heated seat wiring

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by blackburb, Dec 18, 2013.

  1. blackburb

    blackburb Rockstar 100 Posts

    Driver's side isn't heating. Passenger's works fine. Switch lights up when you press it. Anyone know which of the maze of wires under the seat is for the heat?
  2. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    I have a few things for you:
    Here is an Awesome writeup that [MENTION=58304]Jamm3r[/MENTION] did about the heated seats:

    http://www.gmtruckclub.com/forum/sh...stment-system-1999-2006?highlight=heated seat

    Here is a GM bulletin:

    Service Information 2003 tahoe- 2WD | Avalanche, Escalade, Suburban, Tahoe, Yukon (VIN C/K) Service Manual | Document ID: 1864985

    #PIT3287D: Heated Seat Inoperative Or Shuts Off In 30 Seconds - keywords B1825 B2435 B2440 B3606 - (Oct 2, 2006)

    Subject: Heated Seat Inoperative or Shuts Off In 30 Seconds

    Models: 2003-2006 Cadillac Escalade, Escalade ESV, Escalade EXT

    2003-2006 Chevrolet Avalanche, Suburban, Tahoe

    2003-2007 Silverado Classic

    2003-2007 GMC Sierra Classic, Sierra Denali Classic

    2003-2006 Yukon, Yukon Denali, Yukon XL, Yukon Denali XL

    2003-2007 Hummer H2


    The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

    Driver and passenger heated seats inoperative or shut off in 30 seconds. There will be DTCs B2435, B2440, B3606 and/or B1825 set in the Driver seat module. The adjustable pedal position sensor, seat reliner position sensor and both heat seat thermistors share the same 5 volt reference internal to the Drivers Seat Module. A fault in any of these components/circuits can make the heated seats inoperative or shut off in 30 seconds, as well as, the seat recliner and/or adjustment pedals may move in short increments when operated. A fault in heated seats, adjustable pedal or seat recliner will affect BOTH heated seats.

    Note:: Even if the vehicle is not equipped with adjustable pedals DTC B3606 still may set.

    To help isolate the area of concern use the Tech 2 and go to "Sensor Data" in the Drivers Seat Module. Monitor the following parameters for being out of range:

    Recline Position- Normal range .39V-4.58V

    Pedal Position (if equipped) - Normal range .39V-4.58V

    Psgr. Seat heat Sensor- Normal range 1V-4V

    Drvr. Seat Heat Sensor- Normal range 1V-4V

    If a parameter is found to be out of range inspect circuits for any opens, shorts to ground, or voltage. If none found replace the suspect component.

    Please be aware of the following common areas of concern:

    The adjustable pedal sensor internally shorted pulling the 5 volt reference low. Disconnect the adjustable pedal position sensor and see if the heated seats start working correctly, if so replace.
    Note Important:: The APP (Accelerator Pedal Position) sensor is NOT the adjustable pedal position sensor. Make sure the correct sensor, adjustable pedal position sensor, is disconnected.

    The seat recliner position sensor internally shorted pulling the 5 volt reference low. Disconnect the recliner position sensor and see if heated seats start working correctly, if so replace.
    An open in either heated seat thermistor circuits (signal or low reference). The most common is the passenger thermistor where it passes through seat connector C305 pin "L" or "K" or C399 pins "R" or "G".
    A chaff to ground on either heated seat thermistor signal circuits. The most common is circuit 5475 black/red or dark blue shorted to ground in the passenger side near the buckle.
    Note Important:: The heated seat thermistors act differently to "OPENS and SHORTS" than the adjustable pedal position sensor and seat recliner position sensor. The adjustable pedals and seat recliner sensors can be disconnected for testing of the heated seats. Where as the heated seat thermistor circuit must be working correctly before EITHER heated seat will operate. Disconnecting one thermistor, which may have a concern will not allow the opposite heated seat to work correctly, BOTH side must be operational before EITHER heated seat will operate.

    Clearing DTCs

    If DTCs will not clear when using the Tech 2 after a repair has been made, try operating the device in which the repair was made. Example, if a repair was made to the passenger heated seat thermistor circuit, the DTCs may not clear unless the passenger heated seat is operated.

    Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

    GM bulletins are intended for use by professional technicians, NOT a ""do-it-yourselfer"". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

    © 2011 General Motors Corporation. All rights reserved


  3. blackburb

    blackburb Rockstar 100 Posts

    Thanks for the info Pikey. I'm going to have to take a close look at all of it. Unfortunately, Jamm3r's write-up doesn't quite hit my situation. The light at the switch comes on, and stays on, but no heat. All other seat functions work properly including memory and lumbar. I have one of those cigarette lighter plug heated cushions from my old burb, I might just have to throw that on for now.
  4. BurbanMan

    BurbanMan Rockstar 3 Years 500 Posts

    If a person unplugs the switch on one seat, shouldn't the other still work as well? I did this to the drivers seat on my wife's 99 and I noticed the other night that the pass side doesn't work when it did last year...
  5. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    These elements will wear out. But, just to clarify, you have lights and you do not have any heat on the cushion, or on the back.

    If just the cushion, suspect a worn out element.
  6. blackburb

    blackburb Rockstar 100 Posts

    No heat on either the cushion or back on the driver's seat. Yes, the lights come on at the switch in both high and low position and they stay on until you switch off.

    As this truck came from California, I wouldn't be surprised if the heated seats were never used before this winter. I'm sure they could have been at some point, but it's also possible they never were.
  7. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    It's not the use that wears them out, it's just sitting in the seat. But, I would be surprised if both the seat and the back where damaged from sitting.

    The 2nd possibility is a broken wire, or two, in the wiring bundle that runs from the door to the body, the constant opening and closing of the door has been known to damage the wires.

    If I was you, I'd be opening the door to get at the memory module and checking for resistance at the pins for the element wiring.
  8. blackburb

    blackburb Rockstar 100 Posts

    This is why I asked which wires were for the heaters. I was expecting to have to check them under the seat. I didn't know the seat bottom came off separately and fairly easy. I'll pull the seat bottom out so I can check the elements and see if I'm getting voltage and then go from there.

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