OK. Below is a bulletin that may help. You might need to have the system scanned with a scan tool to get codes. Review the data and let me know what you think.
#PIT3287D: Heated Seat Inoperative Or Shuts Off In 30 Seconds - keywords B1825 B2435 B2440 B3606 - (Oct 2, 2006)
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 Drivers Seat Module. The adjustable pedal position sensor, seat recliner 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:
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.
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.
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.
That's going to take me a little time. I'll get back to you with the test results as soon as I have them.
Well, we didn't find anything in the sensor data so we were going to pull the driver seat to check the harness. We disconnected the battery to do so then had to reconnect it just a few minutes later to move the vehicle. When we reconnected the battery everything started working, so now we're waiting for it to happen again to continue diagnosing the problem. Weird...