Chevrolet Silverado / GMC Sierra. Service manual — part 2755

DTC B2435 OR B2440

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 B2435 02

Left Seat Back Heater Sensor Circuit Shorted to Ground

DTC B2435 05

Left Seat Back Heater Sensor Circuit Shorted to Battery or Open

DTC B2440 02

Right Seat Back Heater Sensor Circuit Shorted to Ground

DTC B2440 05

Right Seat Back Heater 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 Back
Element Supply Voltage

B2508 02

B1935 0C

B1935 0D

B2508 01

-

Left Heated Seat Back
Element Control

B2508 02

B1935 0C

B1935 0D

B2508 01

-

Left Heated Seat Back
Temperature Sensor Signal

B2435 02

B1935 04

B1935 1F

B2435 05

B1935 04

B1935 1F

B2435 05

-

Left Heated Seat Back
Temperature Low Reference

-

B1935 04

B1935 1F

B2435 05

-

-

Right Heated Seat Back

B2180 0C

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 back 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 heated seat system must be active.

Conditions for Setting the DTC

B2435 02, B2440 02

The temperature sensor voltage drops below 0.8 volt for more than 1 second.

B2435 05, B2440 05

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

Action Taken When the DTC Sets

The heated seat back 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.

Element Supply Voltage

B2508 02

B2180 0D

B2508 01

-

Right Heated Seat Back
Element Control

B2508 02

B2180 0C

B2180 0D

B2508 01

-

Right Heated Seat Back
Temperature Sensor Signal

B2440 02

B2180 04

B2180 1F

B2440 05

B2180 04

B2180 1F

B2440 05

-

Right Heated Seat Back
Temperature Low Reference

-

B2180 04

B2180 1F

B2440 05

-

-

2008 Chevrolet Silverado 1500

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

Sierra & Silverado

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

Reference Information

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

B2435

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

2. Test for 850-300k ohms between the signal circuit terminal 4 X5 and the low reference

circuit terminal 2 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
back 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 back heater element.

2008 Chevrolet Silverado 1500

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

Sierra & Silverado

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

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

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

and ground.

If greater than the specified range, test the signal circuit for a short to voltage. If the
circuit tests normal, replace the MSM.

If less than the specified range, test the signal circuit for a short to voltage. If the
circuit tests normal, replace the MSM.

6. If all circuits test normal, replace the MSM.

B2440

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

2. Test for 850-300k ohms between the signal circuit terminal 3 X5 and the low reference

circuit terminal 5 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
back 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 back heater element.

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

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

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

and ground.

If greater than the specified range, test the signal circuit for a short to voltage. If the
circuit tests normal, replace the MSM.

If less than the specified range, test the signal circuit for a short to voltage. If the
circuit tests normal, replace the MSM.

6. If all circuits test normal, replace the MSM.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Driver Seat and Passenger Seat Back Cushion Heater Replacement

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

2008 Chevrolet Silverado 1500

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

Sierra & Silverado