DTC B2508 or B2509. GMC Truck Sierra

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra - 2WD 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC B2508 or B2509

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 01: Seat Heater Relay Circuit Short to Battery

DTC B2508 02: Seat Heater Relay Circuit Short to Ground

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
B+ MSM Terminal 5 X3	1, 2, B1935 0C, B1935 0D, B2180 0C, B2180 0D, B2425 0C, B2425 0D, B2430 0C, B2430 0D	1, 2, B1935 0C, B1935 0D, B2180 0C, B2180 0D, B2425 0C, B2425 0D, B2430 0C, B2430 0D	--	--
Driver Heated Seat Back Element Supply Voltage	B2508 02	B1935 0C, B1935 0D	B2345 00, B2508 01	B1935 0B, B1935 0E
Driver Heated Seat Back Element Control	B2345 00, B2508 02	B1935 0C, B1935 0D	B2345 00, B2508 01	B1935 0B, B1935 0E
Driver Heated Seat Back Temperature Sensor Signal	B2435 02	B1935 04, B1935 1F, B2435 0D	B1935 04, B1935 1F, B2435 0D	B1935 0A, B2345 13, B2345 42, B2345 4B
Driver Heated Seat Back Temperature Sensor Low Reference	--	B1935 04, B1935 1F, B2435 0D	--	B2345 13, B2345 42, B2345 4B
Driver Heated Seat Cushion Element Supply Voltage	B2508 02	B2425 0C, B2425 0D	B2345 00, B2508 01	B2425 0B, B2425 0E
Driver Heated Seat Cushion Element Control	B2345 00, B2508 02	B2425 0C, B2425 0D	B2345 00, B2508 01	B2425 0B, B2425 0E
Driver Heated Seat Cushion Temperature Sensor Signal	B1925 02, B2425 1F	B1925 05, B2425 04, B2425 1F	B1925 05, B2425 04, B2425 1F	B2345 13, B2345 42, B2345 4B, B2425 0A
Driver Heated Seat Cushion Temperature Sensor Low Reference	--	B1925 05, B2425 04, B2425 1F	--	B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Back Element Supply Voltage	B2508 02	B2180 0C, B2180 0D	B2345 00, B2508 01	B2180 0B, B2180 0E
Passenger Heated Seat Back Element Control	B2345 00, B2508 02	B2180 0C, B2180 0D	B2345 00, B2508 01	B2180 0B, B2180 0E
Passenger Heated Seat Back Temperature Sensor Signal	B2440 02	B2180 04, B2180 1F, B2440 05	B2180 04, B2180 1F, B2440 05	B2180 0A, B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Back Temperature Sensor Low Reference	--	B2180 04, B2180 1F, B2440 05	--	B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Cushion Element Supply Voltage	B2508 02	B2430 0C, B2430 0D	B2345 00, B2508 01	B2430 0B, B2430 0E
Passenger Heated Seat Cushion Element Control	B2345 00, B2508 02	B2430 0C, B2430 0D	B2345 00, B2508 01	B2430 0B, B2430 0E
Passenger Heated Seat Cushion Temperature Sensor Signal	B2170 02, B2430 1F	B2430 04, B2430 1F, B2170 05	B2430 04, B2430 1F, B2170 05	B2345 13, B2345 42, B2345 4B, B2430 0A
Passenger Heated Seat Cushion Temperature Sensor Low Reference	--	B2430 04, B2430 1F, B2170 05	--	B2345 13, B2345 42, B2345 4B
1. Power seat inoperative 2. Heated seat inoperative

The driver and front 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 MSM will allow heated seat operation, it checks to see if this reference voltage is shorted to ground or battery voltage. Once the MSM 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 MSM must be powered.

Conditions for Setting the DTC

B2508 02

Before the heated seats are activated, the MSM detects a short to ground on the seat heating element supply voltage circuit or control circuit.

B2508 01

Before the heated seats are activated, the MSM detects a short to battery voltage on the seat heating element supply voltage circuit or control circuit.

Action Taken When the DTC Sets

The heated seat function for both seats will be disabled.

Conditions for Clearing the DTC

•	The current DTC clears when the malfunction is no longer present 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

Connector End View Reference

Heated/Cooled Seat Connector End Views

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

DTC Type Reference

DTC Symptom Description

Scan Tool Reference

•	Scan Tool Data List

•	Scan Tool Data Definitions

Circuit/System Testing

Ignition OFF, disconnect the X1, X4 harness connectors at the MSM.
Test for infinite resistance between the supply voltage circuit terminal 14 X1 and ground.

⇒	If not the specified value, test the supply voltage circuit and the control circuits listed below for a short to ground:

•	Driver seat cushion and back element terminal 14 X1

•	Driver seat cushion element terminal 11 X1

•	Driver seat back element terminal 1 X1

Test for infinite resistance between the supply voltage circuit terminal 6 X1 and ground.

⇒	If not the specified value, test the supply voltage circuit and the control circuits listed below for a short to ground:

•	Passenger seat cushion and back element terminal 6 X1

•	Passenger seat cushion element terminal 14 X4

•	Passenger seat back element terminal 4 X1

Ignition ON, verify that a test lamp does not illuminate between the supply voltage circuit terminal 14 X1 and ground.

⇒	If the test lamp illuminates, test the supply voltage circuit and the control circuits listed below for a short to voltage:

•	Driver seat cushion and back element terminal 14 X1

•	Driver seat cushion element terminal 11 X1

•	Driver seat back element terminal 1 X1

Ignition ON, verify that a test lamp does not illuminate between the supply voltage circuit terminal 6 X1 and ground.

⇒	If the test lamp illuminates, test the supply voltage circuit and the control circuits listed below for a short to voltage:

•	Passenger seat cushion and back element terminal 6 X1

•	Passenger seat cushion element terminal 14 X4

•	Passenger seat back element terminal 4 X1

If all circuits test normal, replace the MSM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Driver or Passenger Seat Back Cushion Heater Replacement

•	Driver or Passenger Seat Cushion Heater Replacement

•	Control Module References for the MSM replacement, setup, and programming