Front Heated Seat Malfunction (With Memory A45)
Front Heated Seat Malfunction (With Memory A45)
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
The driver and front passenger heated seats are controlled by separate heated seat switches that are located in the radio/HVAC controls. When a heated seat switch is pressed, a serial message is sent from the radio/HVAC controls to the HVAC control module indicating the heated seat command. The HVAC control module then serves as a gateway to transmit the message to the seat memory control module via the serial data line. In response to this message, the seat memory control module applies battery positive voltage through the element supply voltage circuit to the appropriate seat heating elements. The seat memory control module then sends a serial data message back to the HVAC control module to gateway the information to the radio/HVAC controls to either illuminate or turn off the appropriate temperature indicator.
Reference Information
Schematic Reference
Heated/Cooled Seat Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Heated/Vented Seat Description and Operation (Description and Operation)
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 (Programming and Relearning) for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the X4 harness connector at the K40 seat memory control module.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 5 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Ignition OFF, connect the X4 harness connector at the K40 seat memory control module.
4. Ignition ON, observe the scan tool Driver Seat Heating/Venting/Cooling Mode parameter after pressing the driver HEATED seat switch. The reading should change between Off and Back & Cushion Heat.
• If not the specified value, replace the A20 radio/HVAC controls.
5. Observe the scan tool Passenger Front Seat Heating/Venting/Cooling Mode parameter after pressing the passenger HEATED seat switch. The reading should change between Off and Back & Cushion Heat.
• If not the specified value, replace the A20 radio/HVAC controls.
6. If all scan tool parameter readings test normal, there are no DTCs set, and the driver and/or passenger heated seat is inoperative, replace the K40 seat memory control module.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Radio Control Assembly Replacement (Radio Control Assembly Replacement)
* Control Module References (Programming and Relearning) for seat memory control module replacement, setup, and programming