Heated Seats

DESCRIPTION
OPERATION
DIAGNOSIS AND TESTING - HEATED SEAT SYSTEM

DESCRIPTION

Vehicles with the heated seat option can be visually identified by the two heated seat switches (1) located in the accessory switch pod in the center of the instrument panel (3). The heated seat system allows the driver and front seat passenger to select from two different levels of heat (high and low). The heated seat system for this vehicle includes the following major components:

Heated Seat Pad Elements - Four heated seat pad elements. Two for each front seat. The heater pads are integral to the individual seat bottom and seat back cushions (Refer to 08 - Electrical/8G - Heated/Cooled Systems/Heated Seats/PAD, Heater - Description) .
Heated Seat Module (HSM) - This module contains the control logic and software for the front heated seat system. The module communicates on the Local Interface Network (LIN) data bus.
Heated Seat Switches - Two front heated seat switches. Each switch includes two Light-Emitting Diode (LED) indicator lamps (2) for heat level indication (Refer to 08 - Electrical/8G - Heated/Cooled Systems/Heated Seats/SWITCH, Heated Seat - Description) .
Instrument Cluster (CCN) - The instrument cluster, sometimes referred to as the Cab Compartment Node (CCN) utilizes integrated software and information carried on the LIN data bus. The CCN serves as the link between the heated seat switches and the heated seat module.

OPERATION

The heated seat system operates on battery current received through fused ignition switch output (run) circuits, so that the heated seat system will only operate when the engine is running. The heated seat system will turn off automatically whenever the engine is turned off.

A Heated Seat Module (HSM) is used to control the heated seat system. The HSM responds to heated seat switch messages and ignition switch status inputs by controlling the 12 volt Direct Current (DC) output to the front seat heating elements through integral solid-state relays.

When either of the heated seat switches are pressed, a switch status message is sent to the Cab Compartment Node (CCN) or instrument cluster over the Local Interface Network (LIN) data bus. The CCN then sends a message via the LIN data bus to the HSM, signaling the module to energize the heating element for the selected seat. Amber Light Emitting Diodes (LEDs) in each switch indicate the level of heat in use: Two LEDs are illuminated for high, one for low, and none for off. The HSM sends the LED illumination message to the CCN over the LIN data bus. The CCN then sends the LED illumination message to the accessory switch bank so that the appropriate LEDs are illuminated for any given heating level. Pressing the switch once will select high-level heating. Pressing the switch a second time will select low-level heating. Pressing the switch a third time will shut the heating elements off.

The HSM energizes an integral solid-state relay, which supplies battery current to the heated seat elements. When high-temperature heating is selected, the heating elements provide a boosted heat level during the first four minutes of operation after heating is activated. The heat output then drops to the normal high-temperature level. If high-level heating is selected, the HSM will automatically switch to the low level after two hours of continuous operation. At that time, the number of illuminated LEDs changes from two to one, indicating the change. Operation on the low setting also turns off automatically after two hours.

The heated seat module will automatically turn off the heating elements if it detects an open or low short in the heating element circuit.

DIAGNOSIS AND TESTING - HEATED SEAT SYSTEM

NOTE:
Vehicles equipped with the heated seat option utilize a low voltage cut-off feature. This feature turns off power to the heated seat system anytime vehicle voltage is below 11.7 volts or above 15.5 volts. Be certain to check the vehicle electrical system for proper voltage anytime the heated seat system appears inoperative.

NOTE:
If a Diagnostic Trouble Code (DTC) can not be verified, it is a good indication that an INTERMITTENT fault condition may be present. To help find an intermittent problem, sit in the seat in question and move around the heating elements within the seat while testing continuity. also wiggle the heated seat wire harness and electrical connectors while testing continuity.

NOTE:
For complete circuit diagrams, see Wiring Information. Wiring Information includes wiring diagrams, connector pin-out and location views, details of wire harness routing and retention, splice and ground locations and proper wire and connector repair procedures.

Before testing any individual components in the heated seat system, check the following:

Check the vehicles battery open-circuit voltage and charging system performance. If the vehicle's electrical system is defective or weak it may not be suppling sufficient energy to operate the heated seat system.
Using a scan tool, check for any Diagnostic Trouble Codes (DTCs) related to the Cabin Compartment Node (CCN), Heated Seat Module (HSM) and heated seat switches. If any DTCs are found, repair as necessary (Refer to 28 - DTC-Based Diagnostics/NODE, Cabin Compartment (CCN) - Diagnosis and Testing).
If there are no DTCs and the front heated seat system functions properly, but one or both of the Light Emitting Diode (LED) indicators in a front heated seat switch do not illuminate, replace the accessory switch pod (Refer to 08 - Electrical/8J - Instrument Cluster/POD, Switch - Removal) .