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
- Driver Seat Heater Relay Circuit
DTC B2509
- Front Passenger Seat Heater Relay Circuit
Diagnostic Fault Information
Circuit/System Description
The driver and passenger heated seats are controlled by separate heated seat switches. Both switches are located in the HVAC control module. When a heated seat switch is pressed, the HVAC control module sends a class 2 serial data message to the body control module (BCM) indicating the heated seat command. In response to this signal, the BCM applies battery positive voltage through the heated seat relay control circuit energizing the relay coil. The relay closes its switch contacts applying battery positive voltage through the element supply voltage circuit to the seat heating elements. The BCM then sends a class 2 serial data message back to the HVAC control module to illuminate the appropriate temperature indicator.
Conditions for Running the DTC
* DTC B1327 must not be present.
* Battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
B2508
The DTC will set when the BCM detects a short to ground or voltage in the driver heated seat relay control circuit.
B2509
The DTC will set when the BCM detects a short to ground or voltage in the passenger heated seat relay control circuit.
Actions Taken When the DTC Sets
The heated seat system for the affected seat will be disabled.
Conditions for Clearing the DTC
* The current DTC will clear and set to history 3 seconds after the reference voltage returns to the normal operating range.
* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.
Diagnostic Aids
When DTC B2508 or B2509 are set as current, the BCM disables the heated seat function not allowing any heated seat relay control functions to occur. Cycling the ignition OFF then ON will reset the DTC and allow relay commands.
Reference Information
Schematic Reference
Heated/Cooled Seat Schematics (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 appropriate heated seat relay.
2. Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal C2 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the relay control circuit terminal A1 and ground.
4. Command the appropriate heated seat ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the appropriate heated seat relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning)for BCM replacement, setup, and programming