Front Heated Seat Malfunction (KA1 Without KU1 and KU3)
Front Heated Seat Malfunction (KA1 Without KU1 and KU3)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
When a heated seat switch is pressed, a LIN bus serial data message is sent from the radio/HVAC controls to the HVAC control module. In turn the HVAC control module sends a low speed GMLAN serial data message to the body control module (BCM) indicating the heated seat command. The BCM serves as the heated seat system master to determine the requested operating mode. The BCM then sends a LIN bus serial data message to the seat heating control module indicating the heated seat command. The BCM also controls the seat temperature and mode indicators, via the serial data line, used to provide the operator with feedback as to the operating status of the system.
When the seat heating control module receives a heated seat command, it applies a high side drive pulse width modulated (PWM) signals driven at the required duty cycles to generate the appropriate effective voltage to the heating elements to attain the commanded seat temperature.
Reference Information
Schematic Reference
Heated/Cooled Seat Schematics Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Heated/Vented Seat Description and Operation Heated/Vented Seat
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON.
2. Verify the scan tool Body Control Module Driver Seat Heating Switch parameter changes between Inactive and Active when pressing the heated seat switch.
• If the parameter does not change
Replace the A20 Radio/HVAC Controls.
• If the parameter changes
3. Verify the scan tool Body Control Module Passenger Seat Heating Switch parameter changes between Inactive and Active when pressing the heated seat switch.
• If the parameter does not change
Replace the A20 Radio/HVAC Controls.
• If the parameter changes
4. Verify that both the driver and front passenger heated seats operate.
• If both the driver and front passenger heated seats are inoperative
Refer to Circuit/System Testing - Both Heated Seats are Inoperative
• If just one of the heated seats is inoperative
Refer to Circuit/System Testing - One Heated Seat Inoperative
• If both heated seats operate
5. All OK.
Circuit/System Testing
Both Heated Seats are Inoperative
Note: Circuit/System Verification must be performed before proceeding with Circuit/System Testing.
1. Ignition OFF and all vehicle systems OFF, disconnect the X2 harness connector at the K29F Seat Heating Control Module - Front. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 7 and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Ignition ON.
4. Verify a test lamp illuminates between the B+ circuit terminals listed below and ground.
* Terminal 2
* Terminal 3
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 ohms in the appropriate B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K29F Seat Heating Control Module - Front.
• If the test lamp illuminates
5. Replace the K29F Seat Heating Control Module - Front.
One Heated Seat is Inoperative
Note: Circuit/System Verification must be performed before proceeding with Circuit/System Testing
1. Ignition OFF, disconnect the X2 harness connector at the K29F Seat Heating Control Module - Front, ignition ON.
2. Verify a test lamp illuminates between the B+ circuit terminal 2 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K29F Seat Heating Control Module - Front.
• If the test lamp illuminates
3. Ignition OFF and all vehicle systems OFF, connect the X2 harness connector at the K29F Seat Heating Control Module - Front and disconnect the harness connector at the appropriate E14 Seat Heating Element. It may take up to 2 minutes for all vehicle systems to power down.
4. Test for less than 10 ohms between the ground circuit terminal A and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
5. Ignition ON, connect a test lamp between the control circuit terminal B and ground.
6. Verify the test lamp turns ON and OFF when commanding the appropriate Driver or Passenger Seat Heating element ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the X2 harness connector at the K29F Seat Heating Control Module - Front.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K29F Seat Heating Control Module - Front.
• If the test lamp is always ON
1. Ignition OFF, disconnect the X2 harness connector at the K29F Seat Heating Control Module - Front, ignition ON.
2. Test for less than 1 V between the control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K29F Seat Heating Control Module - Front.
• If the test lamp turns ON and OFF
7. Test or replace the E14 Seat Heating Element.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Front Seat Vent Fan Mat Replacement Front Seat Vent Fan Mat Replacement
* Front Seat Back Cushion Vent Fan Mat Replacement Front Seat Back Cushion Vent Fan Mat Replacement
* Control Module References Control Module References for K20 Radio/HVAC Controls and K29F Seat Heating Control Module - Front replacement, programming and setup