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 driver and passenger seat heating elements are controlled by a common high current relay internal to the heated seat module and by individual low side element control circuits. The heated seat module 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 heated seat module 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 heated seat module must be powered.

Conditions for Setting the DTC

B2508 01

The heated seat module detects a short to voltage on the heater element supply voltage circuit or control circuit.

B2508 02

The heated seat module 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.

Circuit/System Testing

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

^ If not the specified value, test the control circuit for a short to ground.

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

^ If not the specified value, 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. 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 heated seat module.

Repair Instructions

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

* Driver Seat and Passenger Seat Back Cushion Heater Replacement (Impala)
* Driver Seat and Passenger Seat Cushion Heater Replacement (Impala).