Chevrolet Silverado / GMC Sierra. Service manual — part 2757

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The heated seat system operation is controlled through the switch inputs to the driver and
passenger door modules. When a heated seat switch is pressed a GMLAN message is sent to the
memory seat module (MSM) indicating the switch is active. The MSM monitors the heated seat
switch inputs and determines the appropriate operating mode. When a heated seat function is
activated the MSM will send a GMLAN message to the door module to illuminate the
appropriate indicators. The memory seat module controls the voltage supply and the ground
circuits to the seat heater elements. When a heated seat function is commanded active, the seat
module will switch battery voltage to the heater element supply circuits, and ground is provided
through pulse width modulated (PWM) low side drive control circuits. During heated seat
operation both the seat back and cushion heater elements are supplied battery voltage. The seat
module grounds the appropriate control circuits for back only or back and cushion heating modes,
and opens or closes the active control circuits as necessary in order to maintain the desired seat
temperature. The seat module relies on 4 independent inputs from thermistors located in the seat
back and seat cushion of the driver and passenger seats to control heated seat temperatures. The
thermistors are 2-wire sensors supplied with a 5-volt referenced signal circuit and a low reference
circuit from the seat module. Resistance through the thermistors varies with temperature causing
the heated seat sensor signal circuit voltage levels to decrease as the seat temperatures rise.

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

2008 Chevrolet Silverado 1500

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

Sierra & Silverado

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Testing

1. Ignition ON, verify that the driver and passenger door switch heated seat switch parameters

display Active while the heated seat switches are pressed.

If either of the switch parameters are continuously Active or Inactive while the switch
is pressed, perform the heated seat switch circuit test.

2. Verify that the MSM driver and passenger seat HVC mode and level parameters are

displayed correctly as the heated seat switches are activated through all of the operating
modes.

If the MSM parameters are not displayed correctly replace the MSM.

3. If the circuits test normal replace the driver or passenger door module.

Component Testing

1. Disconnect the heated seat switch connector at the door module.

2. Connect a fused jumper wire from the low reference circuit terminal 4 to ground.

3. Verify that a test lamp does not illuminate when connected from battery voltage to the

switch signal circuit terminals 6 and 7.

If the test lamp illuminates while the switches are in an inactive state, replace the
heated seat switch.

4. Verify that a test lamp illuminates when connected from battery voltage to the switch signal

circuit terminals 6 and 7 while pressing the heated seat switches.

If the test lamp does not illuminate while the switches are in an active state, replace the
heated seat switch.

5. Verify that the heated seat switch indicators illuminate with a test lamp connected from

battery voltage to the indicator control circuit terminals 1, 2, 9, 10, and 11.

If the indicators do not illuminate replace the heated seat switch.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

2008 Chevrolet Silverado 1500

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

Sierra & Silverado

Front Seat Heater Switch Replacement (w/o KB6)

Control Module References for MSM and Driver or Passenger Door switch replacement,
programming, and setup

REPAIR INSTRUCTIONS

FRONT SEAT HEATER SWITCH REPLACEMENT (W/O KB6)

Fig. 3: View Of Seat Heater Switch Assembly, Screws & Trim Panel
Courtesy of GENERAL MOTORS CORP.

2008 Chevrolet Silverado 1500

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

Sierra & Silverado

FRONT SEAT HEATER CONTROL MODULE REPLACEMENT

Fig. 4: View Of Front Seat Heater Control Module & Components
Courtesy of GENERAL MOTORS CORP.

Callout

Component Name

1

Front Side Door Trim Panel
Refer to Front Side Door Trim Panel Replacement (YE9) or Front Side
Door Trim Panel Replacement (SLT) .

2

Seat Heater Switch Screw (Qty: 2)

Tighten: 2 N.m (18 lb in)

NOTE:

Refer to Fastener Notice .

3

Seat Heater Switch Assembly
Tip: Disconnect the electrical connector.

Callout

Component Name

2008 Chevrolet Silverado 1500

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

Sierra & Silverado