Pinpoint Test I: The Heated Seat Is Inoperative

Seats

Pinpoint Tests

Pinpoint Test I: The Heated Seat is Inoperative

Normal Operation

The HVAC module includes the heated seat switch buttons and indicators. The heated seat system will function when the HVAC module is on or off. There is a relay box located behind the headlamp switch area containing 2 micro relays for the driver and passenger heated seats. Battery voltage from circuit 1048 (LB/WH) is supplied to the coil and switch of the driver and passenger heated seat relays. When the ignition switch is ON and the engine running, ground is supplied to the driver or passenger heated seat relay coil from the respective heated seat switch in the HVAC module to energize the relay. This closes the relay switch and voltage is supplied to the respective seat's cushion and backrest heater mats. The cushion and backrest heater mats are connected in series circuit with ground supplied to the backrest heater mat, completing the heater mat circuit to heat the seat. If the heated seat switch is on when the ignition switch is turned OFF, the heated seat switch will be on when the ignition switch is turned back ON.

This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- Heated seat switch (part of HVAC module)
- Heated seat relay
- Cushion heater mat
- Backrest heater mat



PINPOINT TEST I: THE HEATED SEAT IS INOPERATIVE

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I1 CHECK THE HEATED SEAT INDICATORS


- Ignition ON.
- Operate both heated switches on.
- Do one or both heated seat switch indicators illuminate?

Yes
If both indicators illuminate, GO to I2.

For driver seat only, Go To Pinpoint Test J Pinpoint Test J: The Heated Seat Is Inoperative - Driver Seat Does Not Heat But The Heated Seat Indicator Illuminates When Pres. For passenger seat only, Go To Pinpoint Test K. Pinpoint Test K: The Heated Seat Is Inoperative - Passenger Seat Does Not Heat But The Heated Seat Indicator Illuminates When P

No
Turn the ignition switch OFF and DISASSEMBLE as necessary to disconnect all of the HVAC module electrical connectors. WAIT one minute to allow the system to reset and RECONNECT the electrical connectors. RETEST the system. If the heated seat indicator still does not illuminate, INSTALL a new HVAC module. TEST the system for normal operation.

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I2 CHECK VOLTAGE TO THE HEATED SEAT RELAY


- Ignition OFF.
- Disconnect: Heated Seat Relay Driver or Passenger.
- Ignition ON.
- Measure voltage between:
- heated seat relay socket pin 1, circuit 1048 (LB/WH) and ground.
- heated seat relay socket pin 3, circuit 1048 (LB/WH) and ground.




- Are both voltages greater than 10 volts?

Yes
VERIFY the climate control system is operating correctly, REFER to Heating and Air Conditioning.

No
VERIFY Bussed Electrical Center (BEC) fuse 66 (25A) is OK. If OK, REPAIR the circuit. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. TEST the system for normal operation.

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