Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | 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: Driver Seat Heater Relay CircuitDTC B2509: Front Passenger Seat Heater Relay Circuit
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Heated Seat Relay B+ | 1, B1920, B2165 | 1, B1920, B2165 | -- | -- |
Heated Seat Relay Control | 1, B2508, B2509 | B2508, B2509 | B2508, B2509 | -- |
Heated Seat Relay Ground | -- | B2508, B2509 | -- | -- |
Heated Seat Cushion Temperature Sensor Signal | B1925, B2170 | B1920, B2165 | B1920, B1925, B2165, B2170 | -- |
Heated Seat Cushion Temperature Sensor Low Reference | -- | 1, B1920, B2165 | -- | -- |
Heated Seat Heater Element Control | 1, B1920, B2165 | 1, B1920, B2165 | -- | -- |
Heated Seat Element Ground | -- | 1, B1920, B2165 | -- | -- |
1. Front heated seat malfunction | ||||
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 V. |
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 fault-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
Connector End View Reference
Description and Operation
Heated Seats Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the appropriate heated seat relay.
- Test for less than 5.0 Ω between the ground circuit terminal C2 and ground.
- Connect a test lamp between the control circuit terminal A1 and ground.
- Ignition ON, command the appropriate Driver or Passenger Heated Seat ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the a heated seat relay.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | 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. |
Component Testing
Relay Test
- Ignition OFF, disconnect the appropriate heated seat relay.
- Test for 70-100 Ω between terminals 85 and 86.
- Test for infinite resistance between the terminals listed below:
- Install a 10 A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.
| ⇒ | If the resistance is not within the specified range, replace the relay. |
| • | 30 and 85 |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the heated seat relay. |
| ⇒ | If greater than the specified range, replace the heated seat relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
