B2509

DTC B2508 or B2509

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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 Shorted to Battery or Open

DTC B2508 02
- Seat Heater Relay Circuit Shorted to Ground

Diagnostic Fault Information






Circuit/System Description

The front seat heating elements are controlled by a common high current relay internal to the Memory Seat Module (MSM) and on the low side by individual element control circuits. The module connects the heated seat heater element supply voltage circuits to a common reference point. This reference point is biased to approximately 2.0 volts. Before the module will allow heated seat operation, it checks to see if the heating element supply voltage circuits and control circuits are shorted to ground or battery voltage. Once the module verifies that it is not closing into a shorted heating element, it allows heated seat operation. After which it continues to monitor for a shorted circuit.

Conditions for Running the DTC

The MSM must be powered.

Conditions for Setting the DTC

B2508 02

Before the heated seats are activated, the MSM detects a short to ground on the seat heating element supply voltage circuit or control circuit.

B2508 01

Before the heated seats are activated, the MSM detects a short to battery voltage on the seat heating element supply voltage circuit or control circuit.

Action Taken When the DTC Sets

The heated seat function for both seats will be disabled.

Conditions for Clearing the DTC

* The current DTC clears when the malfunction is no longer present and the power mode changes to OFF then back to ACC or RUN.
* The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred.

Circuit/System Testing

1. Ignition OFF, disconnect the X1, X4 harness connectors at the MSM.
2. Test for infinite resistance between the driver seat heating element supply voltage circuit terminal 14 X1 and ground.

^ If less than the specified range, test the supply voltage circuit and the seat cushion and seat back heating element control circuits for a short to ground.

3. Ignition ON, verify that a test lamp does not illuminate between the supply voltage circuit terminal 14 X1 and ground.

^ If the test lamp illuminates, test the supply voltage circuit and the seat cushion and seat back heating element control circuits for a short to voltage.

4. Test for infinite resistance between the passenger seat heating element supply voltage circuit terminal 6 X1 and ground.

^ If less than the specified range, test the supply voltage circuit and the seat cushion and seat back heating element control circuits for a short to ground.

5. Ignition ON, verify that a test lamp does not illuminate between the supply voltage circuit terminal 6 X1 and ground.

^ If the test lamp illuminates, test the supply voltage circuit and the seat cushion and seat back heating element control circuits for a short to voltage.

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Driver Seat and Passenger Seat Back Cushion Heater Replacement
* Driver Seat and Passenger Seat Cushion Heater Replacement