B2509

DTC B2508 or B2509

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




Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview

CIRCUIT/SYSTEM DESCRIPTION
The driver and 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 memory seat module 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 memory seat module (MSM) must be powered.

CONDITIONS FOR SETTING THE DTC

B2508 01
Before the heated seats are activated, the memory seat module 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 memory seat module 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.

CIRCUIT/SYSTEM TESTING
1. Ignition OFF, disconnect the (C1, C4) harness connectors at the MSM.
2. Test for infinite resistance between the driver seat heating element supply circuit terminal 14 (C1) and ground.
- If less than infinite, 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 14 (C1) and ground.
- If the test lamp illuminates, test the seat back and cushion 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 6 (C1) and ground.
- If less than infinite, 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 6 (C1) 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 memory seat module.

REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
- Seat Back Heater Element Replacement - Front
- Seat Cushion Heater Element Replacement - Front
- Control Module References for the memory seat module replacement, programming and setup Programming and Relearning