For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Driver Heated Seat Element Control Terminal 3 X2 | B242A 02 | B2425 0D | B242A 01 | B2425 0E
Driver Heated Seat Element Control Terminal 1 X2 | B242A 02 | B2425 0D | B242A 01 | B2425 0E
Driver Heated Seat Cushion Temperature Sensor Signal | B1925 02 | B1925 05 | B1925 05 | B2345 13
Driver Heated Seat Cushion Temperature Sensor Low Reference | -- | B1925 05 | -- | B2345 13
Passenger Heated Seat Element Control Terminal 5 X2 | B242A 02 | B2430 0D | B242A 01 | B2430 0E
Passenger Heated Seat Element Control Terminal 2 X2 | B242A 02 | B2430 0D | B242A 01 | B2430 0E
Passenger Heated Seat Cushion Temperature Sensor Signal | B2170 02 | B2170 05 | B2170 05 | B2345 13
Passenger Heated Seat Cushion Temperature Sensor Low Reference | -- | B2170 05 | -- | B2345 13

### Circuit/System Description

The driver and passenger heated seats are controlled by a single heated seat module that is located under the driver seat cushion. Both heated seats are controlled by separate heated seat switches that are located in the HVAC control. When a heated seat switch is pressed, the HVAC control sends a message via LIN-Bus to the HVAC control module. The HVAC control module then serves as a gateway to transmit the message to the heated seat module via GMLAN serial data indicating the heated seat command. In response to this signal, the heated seat module then applies battery positive voltage through the element supply voltage circuit to the appropriate seat heating elements. The heated seat module then sends a serial data message back to the HVAC control module to gateway the information to the HVAC control to either illuminate or turn off the appropriate temperature indicator.

### Reference Information

#### Schematic Reference

Heated/Cooled Seat Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Heated Seats Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the scan tool HVAC Driver Heated Seat Sw. parameter while pressing the driver HEATED seat switch. The readings should change between Inactive and Active.

⇒ | If not the specified value, replace the A26 HVAC control.

2. Observe the scan tool HVAC Pass. Heated Seat Sw. parameter while pressing the passenger HEATED seat switch. The readings should change between Inactive and Active.

⇒ | If not the specified value, replace the A26 HVAC control.

3. If all scan tool readings are normal, there are no DTCs set, and the driver and/or passenger heated seat is inoperative, replace the K29 heated seat module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heater and Air Conditioning Control Replacement

• | Control Module References for heated seat module replacement, setup, and programming