B2509

DTC B2508 or B2509

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (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.



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 front passenger heated seat heating elements are controlled by a common high current relay internal to the memory seat module (MSM) and the low side by individual 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 2.0 volts. Before the MSM will allow heated seat operation, it checks to see if this reference voltage is shorted to ground or battery voltage. Once the MSM verifies that it is not closing to 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 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.

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.


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 set the code to history, 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 ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Heated Seats Description and Operation (Description and Operation)
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)


Circuit/System Testing

1. Ignition OFF, disconnect the X1 and X4 harness connectors at the MSM.
2. Ignition OFF, test for infinite resistance between the driver seat heating element supply circuit terminal 6 and ground.

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

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

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

4. Test for infinite resistance between the passenger seat heating element supply voltage circuit terminal 14 and ground.

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

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

• If the test lamp illuminates, test the seat cushion and seat back heating element supply voltage circuits and element 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 Seat Back Cushion Heater and Passenger Seat Back Cushion Heater Replacement (Driver Seat Back Cushion Heater and Passenger Seat Back Cushion Heater Replacement)
* Driver Seat Cushion Heater and Passenger Seat Cushion Heater Replacement (Driver Seat) (Driver Seat Cushion Heater and Passenger Seat Cushion Heater Replacement (Driver Seat))Driver Seat Cushion Heater and Passenger Seat Cushion Heater Replacement (Passenger Seat) (Driver Seat Cushion Heater and Passenger Seat Cushion Heater Replacement (Passenger Seat))
* Control Module References (Programming and Relearning) for MSM replacement, setup, and programming