Heated Seat Inoperative
Heated Seat Inoperative
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (with HP2) (Initial Inspection and Diagnostic Overview)Diagnostic System Check - Vehicle (without HP2) (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 front passenger heated seats are controlled by separate heated seat switches located on the door panels. When a heated seat switch is pressed, ground is momentarily applied through the switch contacts and the switch signal circuit to the door lock/window switch. In response to this signal, the door lock/window switch sends a serial message to the memory seat module (MSM) or heated seat module (HSM) indicating the heat seat request. The module then applied battery voltage to the seat cushion and seat back heater elements through a common voltage supply circuit. Each individual heater element is grounded by the module through separate low side drive control circuits. The heater element control circuits are pulse width modulated (PWM) to ground by the module in order to control the seat temperatures by regulating the current flow through the heater elements. The MSM/HSM relies on 4 independent inputs from temperature sensors (thermistors) located in the seat back and seat cushion of the driver and passenger seats. The temperature sensor resistance varies based on the temperature of the heating element causing the signal circuit voltage to change. Once the seat reaches the switch set temperature, the MSM/HSM will then cycle the control circuits of the heating elements ON and OFF in order to maintain the desired seat temperature based on the feedback voltage from the sensors. The MSM/HSM then monitors the current flow through the heating elements and the of rate change of the temperature sensor to verify correct heated seat operation.
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 (KA1) (Heated Seats Description and Operation (KA1))Heated Seats Description and Operation (KA6) (Heated Seats Description and Operation (KA6))
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) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the appropriate scan tool Driver Door Switch or Passenger Door Switch parameters listed below while pressing and releasing the appropriate switch. The readings should change between Inactive and Active.
* Seat Back Heat Mode Sw.
* Seat Heat Mode Sw.
• If not the specified values, refer to the Heated Seat Switch component test. If the heated seat switch tests normal, test or replace the appropriate door lock/window switch.
2. If all scan tool parameters test normal and there are no DTCs set, replace the MSM/HSM.
3. If all heated seat functions operate normal and the heated seat switch indicators do not illuminate, refer to the Heated Seat Switch Indicators component test.
Component Testing
Heated Seat Switch
1. Ignition OFF, disconnect the X4 harness connector at the door lock/window switch.
2. Test for infinite resistance between the signal circuits listed below and the low reference circuit terminal 4 with the switch in the open position.
* Seat back and cushion heat mode terminal 6
* Seat back only mode terminal 7
• If not the specified value, replace the heated seat switch.
3. Test for less than 2 Ohms between the signal circuits listed below and the low reference circuit terminal 4 with the switch in the closed position.
* Seat back and cushion heat mode terminal 6
* Seat back only mode terminal 7
• If greater than the specified range for any of the tests, replace the heated seat switch.
Heated Seat Switch Indicators
1. Ignition OFF, disconnect the X4 harness connector at the door lock/window switch.
2. Connect a 3 A fused jumper wire between the low reference circuit terminal 4 and ground.
3. Connect a test lamp between B+ and each control circuit listed below. The appropriate indicator should illuminate.
* Seat back and cushion mode indicator terminal 10
* Seat back only mode indicator terminal 11
* Low heat indicator terminal 9
* Medium heat indicator terminal 1
* High heat indicator terminal 2
• If any indicator does not illuminate, replace the heated seat switch.
4. If all indicators illuminate, replace the door lock/window switch.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Front Seat Heater Switch Replacement (Front Seat Heater Switch Replacement)
* Control Module References (Programming and Relearning) for MSM, HSM and driver or passenger door lock/window switch replacement, programming, and setup