B2509

DTC B2508 or B2509

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.

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/System Description

The driver and passenger seat heating elements are controlled by a common high current relay internal to the memory seat module (MSM) and by individual low side element control circuits. The MSM connects the heated seat heater element supply voltage circuits for both seats to a common reference point. This reference point is biased to approximately 2.5 V. Before the MSM will allow heated seat operation, it checks to see if this reference voltage is shorted to ground or voltage. Once the module verifies that it is not closing to a shorted heating element, it allows for heated seat operation. The module will then continue to monitor the heating elements for a shorted circuit.

Conditions for Running the DTC

The MSM must be powered.

Conditions for Setting the DTC

B2508 01

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

B2508 02

The MSM detects a short to ground 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 (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
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 X1, X4 harness connectors at the MSM.
2. Test for infinite resistance between the control circuit terminal 6 X1 and ground.

• If not the specified value, test the control circuits for a short to ground.

3. Test for infinite resistance between the control circuit terminal 14 X1 and ground.

• If not the specified value, test the control circuits for a short to ground.

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

• If the test lamp illuminates, test the control circuits for a short to voltage.

5. Verify that a test lamp does not illuminate between the control circuit terminal 14 X1 and ground.

• If the test lamp illuminates, test the control circuits for a short to voltage.

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

Repair Instructions

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

* Driver or Passenger Seat Back Cushion Heater Replacement (KA1) (Driver or Passenger Seat Back Cushion Heater Replacement (KA1))
* Driver Seat Cushion Heater Replacement (KA1) (Driver Seat Cushion Heater Replacement (KA1))
* Passenger Seat Cushion Heater Replacement (KA1) (Passenger Seat Cushion Heater Replacement (KA1))
* Control Module References (Programming and Relearning) for MSM replacement, setup, and programming