Check the grounds on the frame, inside that front body mount under the drivers door. Corrosion of some kind could be playing a part in that.
Dash grounds are found on either side of the dash, above the side kick panels. Not easy to find.
Heater issues are probably the door actuators, as was posted earlier. Another possibility is the head unit is bad.
Trent has the right idea on the starting/lighting/radio playing issue. Bad door switch would cause all three of those.
Seat problems could probably be traced back to a bad/shorted ground lead or possibly one or more of the elements has an open circuit in them.
Found the Bulletin on the seat heater issue:
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03-05 Chevrolet/GMC/Cadillac All Full Size Trucks and Utilities Heated Seat Inoperative or Shut Off in 30 Seconds B1825 B2435 B2440 B3606 #PIT3287 - (Nov 23, 2004)
03 - 05 Chevrolet/GMC/Cadillac All Full Size Trucks and Utilities Heated Seat Inoperative or Shut Off in 30 seconds B1825 B2435 B2440 B3606.
The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.
Condition/Concern:
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 either heated seats, adjustable pedal or seat recliner will affect BOTH heated seats.
Recommendation/Instructions:
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:
1. The adjustable pedal position 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.
2. 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.
3. 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".
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 diagnosis 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. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
Models:
(03-05 Chevrolet All Full Size Trucks and Utilities) and (03-05 GMC All Full Size Trucks and Utilities) and (03-05 Cadillac All Full Size Utilities)
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