Chevrolet Silverado / GMC Sierra. Service manual — part 2750

DIAGNOSTIC STARTING POINT - SEATS

Begin the system diagnosis with the Diagnostic System Check - Vehicle . The Diagnostic
System Check will provide the following information:

The identification of the control modules which command the system.

The ability of the control modules to communicate through the serial data circuit.

The identification of any stored diagnostic trouble codes (DTCs) and their status.

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the
system and where the procedure is located.

DTC B1925 OR B2170

Diagnostic Instructions

B2425 1F: Left Seat Cushion Heater Circuit Intermittent

B2430 04: Right Seat Cushion Heater Circuit Open

B2430 0A: Right Seat Cushion Heater Circuit Rate of Change

Below Threshold

B2430 0B: Right Seat Cushion Heater Circuit Current Above

Threshold

B2430 0C: Right Seat Cushion Heater Circuit Current Below

Threshold

B2430 0D: Right Seat Heater Cushion Circuit Resistance

Above Threshold

B2430 0E: Right Seat Heater Cushion Circuit Resistance

Below Threshold

B2430 1F: Right Seat Cushion Heater Circuit Intermittent

DTC B2435 or B2440

B2435 02: Left Seat Back Heater Sensor Circuit Shorted to

Ground

B2435 05: Left Seat Back Heater Sensor Circuit Shorted to

Battery or Open

B2440 02: Right Seat Back Heater Sensor Circuit Shorted to

Ground

B2440 05: Right Seat Back Heater Sensor Circuit Shorted to

Battery or Open

DTC B2508 or B2509

B2508 01: Seat Heater Relay Circuit Shorted to Battery or

Open

B2508 02: Seat Heater Relay Circuit Shorted to Ground

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Seat Heating and Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

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 B1925 02

Left Seat Heater Cushion Sensor Circuit Shorted to Ground

DTC B1925 05

Left Seat Heater Cushion Sensor Circuit Shorted to Battery or Open

DTC B2170 02

Right Seat Heater Cushion Sensor Circuit Shorted to Ground

DTC B2170 05

Right Seat Heater Cushion Sensor Circuit Shorted to Battery or Open

Diagnostic Fault Information

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Left Heated Seat Cushion
Element Supply Voltage

B2508 02

B2425 0C

B2425 0D

B2508 01

-

Left Heated Seat Cushion
Element Control

B2508 02

B2425 0C

B2425 0D

B2508 01

-

Left Heated Seat Cushion
Temperature Sensor Signal

B1925 02

B1925 05
B2425 04

B2425 1F

B1925 05
B2425 04

B2425 1F

-

Left Heated Seat Cushion
Temperature Low Reference

-

B1925 05
B2425 04

B2425 1F

-

-

Right Heated Seat Cushion
Element Supply Voltage

B2508 02

B2430 0C

B2430 0D

B2508 01

-

Right Heated Seat Cushion
Element Control

B2508 02

B2430 0C

B2430 0D

B2508 01

-

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Seat Heating and Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Circuit/System Description

The heated seat temperature sensor is located in the seat cushion just under the seat cover with the
seat heating element. The temperature sensor is a 2 wire thermistor and resistance through the
sensor varies with temperature. The signal circuit is referenced from 5 volts within the module
and the temperature of the seat surface determines the signal circuit voltage. Once the seat reaches
the set temperature, the module will then cycle the control circuits of the heating elements ON
and OFF in order to maintain the desired seat temperature based on the feedback voltage from the
sensors.

Conditions for Running the DTC

The memory seat module must be powered.

Conditions for Setting the DTC

B1925 02, B2170 02

The temperature sensor voltage drops below 0.80 volt for more than 1 second.

B1925 05, B2170 05

The temperature sensor voltage is greater than 5 volts for more than 1 second.

Action Taken When the DTC Sets

The heated seat cushion function for the affected seat will be disabled.

Conditions for Clearing the DTC

The current DTC will clear 3 seconds after the reference voltage returns to normal operating
range, and the ignition is cycled OFF then back to ACC or RUN.

A history DTC will clear after 50 ignition cycles or with a scan tool using the clear DTCs
function.

Reference Information

Right Heated Seat Cushion
Temperature Sensor Signal

B2170 02

B2170 05
B2430 04

B2430 1F

B2170 05
B2430 04

B2430 1F

-

Right Heated Seat Cushion
Temperature Low Reference

-

B2170 05
B2430 04

B2430 1F

-

-

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Seat Heating and Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Schematic Reference

Heated/Cooled Seat Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Heated Seats Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

B1925

1. Ignition OFF, disconnect the X2, X5 harness connectors at the MSM.

2. Test for 850-300k ohms between the signal circuit terminal 1 X5 and the low reference

circuit terminal 3 X2.

If greater than the specified range, test the signal circuit and low reference circuit for a
short to voltage or an open/high resistance. If the circuit tests normal, replace the seat
cushion heater element.

If less than the specified range, test for a short between the signal and low reference
circuits. If the circuit tests normal, replace the seat cushion heater element.

3. Connect the X2, X5 harness connectors at the MSM.

4. Disconnect the harness connector at the seat cushion heater element.

5. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal C

and ground.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Seat Heating and Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado