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.

### DTC Descriptors

DTC B2508 01: Seat Heater Relay Circuit Short to Battery
DTC B2508 02: Seat Heater Relay Circuit Short to Ground

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Driver Heated Seat Element Supply Voltage | B2345 00, B2508 02 | B2425 0C, B2425 0D | B2345 00, B2508 01 | --
Driver Heated Seat Element Control | B2345 00, B2508 02 | B2425 0C, B2425 0D | B2345 00, B2508 01 | --
Driver Heated Seat Temperature Sensor Signal | B1925 02 | B1925 05, B2425 04, B2425 1F | B1925 05, B2425 04, B2425 1F | B2345 13, B2345 42, B2345 4B
Driver Heated Seat Temperature Sensor Low Reference | -- | B1925 05, B2425 04, B2425 1F | -- | B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Element Supply Voltage | B2345 00, B2508 02 | B2430 0C, B2430 0D | B2345 00, B2508 01 | --
Passenger Heated Seat Element Control | B2345 00, B2508 02 | B2430 0C, B2430 0D | B2345 00, B2508 01 | --
Passenger Heated Seat Temperature Sensor Signal | B2170 02 | B2170 05, B2430 04, B2430 1F | B2170 05, B2430 04, B2430 1F | B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Temperature Sensor Low Reference | -- | B2170 05, B2430 04, B2430 1F | -- | B2345 13, B2345 42, B2345 4B

### Circuit/System Description

The driver and passenger seat heating elements are controlled by a common high current relay internal to the heated seat module (HSM) and by individual low side element control circuits. The HSM connects the heater element supply voltage circuits for both seats to a common reference point. This reference point is biased to approximately 2.0 volts. Before the HSM will allow heated seat operation, it checks to see if the heating element supply voltage circuits and control circuits are shorted to ground or voltage. Once the HSM verifies that it is not closing to a shorted heating element, it allows for heated seat operation. The HSM will then continue to monitor the heating elements for a shorted circuit.

### Conditions for Running the DTC

The HSM must be powered.

### Conditions for Setting the DTC

#### B2508 01

The HSM detects a short to voltage on the heater element supply voltage circuit or control circuit.

#### B2508 02

The HSM detects a short to ground for on the heater element supply voltage circuit or control circuit.

### Action Taken When the DTC Sets

The heated seat function for both the driver and passenger seats will be disabled.

### Conditions for Clearing the DTC

• | The current DTC will clear and set a history code 3 seconds after the reference voltage returns to normal operating range and the ignition is cycled OFF then back to ACC or RUN.

• | The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred.

### 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 Testing

1. Ignition OFF, disconnect the X1 harness connector at the HSM.
2. Test for infinite resistance between the control circuit terminal 3 and ground.

⇒ | If less than the specified range, test the control circuit for a short to ground.

3. Test for infinite resistance between the control circuit terminal 6 and ground.

⇒ | If less than the specified range, test the control circuit for a short to ground.

4. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 3 and ground.

⇒ | If the test lamp illuminates, test the control circuit for a short to voltage.

5. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 6 and ground.

⇒ | If the test lamp illuminates, test the control circuit for a short to voltage.

6. If all circuits test normal, replace the HSM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Driver or Passenger Seat Back Cushion Heater Replacement

• | Driver or Passenger Seat Cushion Heater Replacement

• | Control Module References for HSM replacement, setup, and programming