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 left and right rear heated seat heating elements are controlled by a common high current relay internal to the rear heated seat module (RHSM) and the low side by individual element control circuits. The RHSM 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 RHSM will allow heated seat operation, it checks to see if this reference voltage is shorted to ground or battery voltage. Once the module 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 RHSM must be powered.
Conditions for Setting the DTC
B2508 01
Before the heated seats are activated, the RHSM 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 RHSM 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 the left and right rear passenger seats 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 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.
Reference Information
Schematic Reference
Heated/Cooled Seat Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Rear Heated Seats Description and Operation (Rear Heated Seats 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 harness connector at the RHSM.
2. Test for infinite resistance between the control circuit terminal 3 and ground.
• If not the specified value, test the control circuits listed below for a short to ground.
* Left rear seat cushion and back element terminal 3
* Left rear seat cushion element terminal 5
* Left rear seat back element terminal 1
3. Test for infinite resistance between the control circuit terminal 6 and ground.
• If not the specified value, test the control circuits listed below for a short to ground.
* Right rear seat cushion and back element terminal 6
* Right rear seat cushion element terminal 2
* Right rear seat back element terminal 4
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 circuits listed below for a short to voltage.
* Left rear seat cushion and back element terminal 3
* Left rear seat cushion element terminal 5
* Left rear seat back element terminal 1
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 circuits listed below for a short to voltage.
* Right rear seat cushion and back element terminal 6
* Right rear seat cushion element terminal 2
* Right rear seat back element terminal 4
6. If all circuits test normal, replace the RHSM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Rear Seat Cushion Heater Replacement (Rear Seat Cushion Heater Replacement)
* Rear Seat Back Cushion Heater Replacement (Rear Seat Back Cushion Heater Replacement)
* Control Module References (Programming and Relearning) for RHSM replacement, setup, and programming