Tahoe 2WD V8-6.0L Hybrid (2008)
Seat Heater: Symptom Related Diagnostic Procedures
Symptoms - Seat Heating and Cooling
Symptoms - Seat Heating and Cooling
Important: The following steps must be completed before using the symptom tables.
1. Perform the Diagnostic System Check - Vehicle before using the Symptom Tables in order to verify that all of the following are true:
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There are no DTCs set.
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The control modules can communicate via the serial data link. See: Testing and Inspection/Initial Inspection and Diagnostic
Overview/Diagnostic System Check - Vehicle
2. Review the system operation in order to familiarize yourself with the system functions. Refer to the following system descriptions:
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Heated Seats Description and Operation (KA1) Heated Seats Description and Operation (KA6)
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Heated/Cooled Seats Description and Operation
Visual/Physical Inspection
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Inspect for aftermarket devices which could affect the operation of the system.
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Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections.
See: Testing and Inspection/Component Tests and General Diagnostics
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:
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Heated Seat Inoperative (Chevy and GMC) Heated Seat Inoperative (Cadillac)
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Heated Seat Inoperative - Rear
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Heated/Cooled Seats Inoperative
Heated Seat Inoperative (Chevy and GMC)
Heated Seat Inoperative (Chevy and GMC)
Diagnostic Instructions
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Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and
Diagnostic Overview/Diagnostic System Check - Vehicle
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Review Strategy Based Diagnosis for an overview of the diagnostic approach.
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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 modulation (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.
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
