Front Heated Seat Malfunction
Front Heated Seat Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The driver and passenger heated seats are controlled by separate heated seat switches. Both switches are located in the HVAC control module. When a heated seat switch is pressed, the HVAC control module sends a class 2 serial data message to the body control module (BCM) indicating the heated seat command. In response to this signal, the BCM applies battery positive voltage through the heated seat relay control circuit energizing the relay coil. The relay closes its switch contacts applying battery positive voltage through the element supply voltage circuit to the seat heating elements. The BCM then sends a class 2 serial data message back to the HVAC control module to illuminate the appropriate temperature indicator.
Reference Information
Schematic Reference
Heated/Cooled Seat Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Heated Seats Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning)
Circuit/System Verification
1. Ignition ON, observe the scan tool driver heated seat parameter while turning the driver seat heater switch ON and OFF. The reading should change between OFF, LOW, and HIGH.
• If the reading does not change between the commanded states, refer to Heated Seat Switch Malfunction.
2. Ignition ON, observe the scan tool passenger heated seat parameter while turning the driver seat heater switch ON and OFF. The reading should change between OFF, LOW, and HIGH.
• If the reading does not change between the commanded states, refer to Heated Seat Switch Malfunction.
Circuit/System Testing
Heated Seat Malfunction
1. Ignition OFF, disconnect the appropriate heated seat relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal C1 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal A2 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal C1 for a short to ground.
4. Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal C2 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
5. Connect a test lamp between the relay control circuit terminal A1 and ground.
6. Command the appropriate heated seat ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
7. Ignition OFF, disconnect the harness connector at the appropriate heated seat back element.
8. Test for less than 5.0 ohms of resistance between the ground circuit terminal B and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
9. Connect the harness connector at the heated seat back element.
10. Ignition OFF, disconnect the harness connector at the appropriate heated seat cushion element.
11. Test for less than 5.0 ohms of resistance between the voltage supply circuit terminal D and ground.
• If greater than the specified range, test the voltage supply circuit for an open/high resistance. If the circuit tests normal, test or replace the heated seat back element.
12. Test for less than 5.0 ohms of resistance between terminal A and terminal D.
• If greater than the specified range, test or replace the heated seat cushion element.
13. Connect the harness connector at the heated seat cushion element.
14. Test for less than 5.0 ohms of resistance between the relay controlled output circuit terminal C1 and ground.
• If greater than the specified range, test the relay controlled output circuit for an open/high resistance.
15. If all circuits test normal, test or replace the appropriate heated seat relay.
Heated Seat Switch Malfunction
1. Ignition ON, observe the scan tool driver heated seat parameter while turning the driver seat heater switch ON and OFF. The reading should change between OFF, LOW, and HIGH.
• If the reading does not change as the switch is activated, replace the HVAC control module.
2. Ignition ON, observe the driver heated seat LOW and HIGH indicators while turning the driver seat heater switch to the LOW and HIGH positions. The indicators should turn ON and OFF as the switch is activated.
• If either the LOW or HIGH indicators does not illuminate, replace the HVAC control module.
3. Ignition ON, observe the scan tool passenger heated seat parameter while turning the driver seat heater switch ON and OFF. The reading should change between OFF, LOW, and HIGH.
• If the reading does not change as the switch is activated, replace the HVAC control module.
4. Ignition ON, observe the passenger heated seat LOW and HIGH indicators while turning the passenger seat heater switch to the LOW and HIGH positions. The indicators should turn ON and OFF as the switch is activated.
• If either the LOW or HIGH indicators does not illuminate, replace the HVAC control module.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Driver Seat and Passenger Seat Back Cushion Heater Replacement (Driver Seat and Passenger Seat Back Cushion Heater Replacement)
* Driver Seat and Passenger Seat Cushion Heater Replacement (Driver Seat and Passenger Seat Cushion Heater Replacement)
* Control Module References (Programming and Relearning) for BCM and HVAC control module replacement, setup, and programming