Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Battery positive voltage is supplied to the heated seat module (HSM) from the HTD SEATS/BCK UP and HTD/SEAT fuses located in the underhood fuse block. When commanded ON, the HSM uses this voltage to heat the seat heating elements. The HSM and the seat heating elements are grounded through the module ground circuit to G301 and G302.

Each time the heated seat switch is pressed, B+ is supplied to the HSM through the heated seat signal circuit. The module counts these inputs to determine what level of heat the vehicle operator is commanding. In response to these switch signals, the HSM sends a B+ signal to illuminate the appropriate heated seat indicator. The HSM then closes it's contacts and applies B+ through the heated seat element supply voltage circuit to the seat heating elements. When the thermistor inside the seat cushion reaches a certain resistance, the control module open and close the supply voltage in order to maintain that heat level.

Schematic Reference

Connector End View Reference

Power Seat Connector End Views

Electrical Information Reference

1. Ignition ON, cycle the heated seat switch between the high and low position. The heated seats should operate in both positions.

⇒	If the heated seats do not operate, refer to Heated Seats Inoperative.

2. Cycle the heated seat switch between the high and low position. The appropriate heated seat indicator should illuminate.

⇒	If either indicator does not illuminate refer to Headed Seat Indicator Inoperative.

Heated Seats Inoperative

1. Ignition OFF, disconnect the harness connector at the appropriate HSM.
2. Test for less than 5 ohms between the ground circuit terminal 2 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 10 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. Verify that a test lamp illuminates between the ignition circuit terminal 3 and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

5. Install a test lamp between the control circuit terminal 9 and B+.
6. Press and release the heated seat switch. The test lamp should turn ON and OFF when the switch is pressed and released.

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit test normal, replace the HVAC control module.

⇒	If the test lamp is always ON, test the control circuit for an short to ground. If the circuit test normal replace the HVAC control module.

7. Test for 1200-15K ohms between the signal circuit terminal 12 and the ground circuit terminal 11.

⇒	If greater than the specified range, test the signal circuit and the ground circuit for a short to voltage or an open/high resistance. If the circuits test normal, replace the seat temperature sensor.

⇒	If less than the specified range, test for a short between the signal circuit and the ground circuit. If the circuits test normal, replace the seat temperature sensor.

8. Ignition OFF, connect the harness connector at the HSM and disconnect the harness connector at the seat back heater element.
9. Test for 2.5-6.5 ohms between terminal A and terminal B.

⇒	If not within the specified range, replace the seat back heater element.

10. Connect the harness connector at the seat back heater element and disconnect the harness connector at the seat cushion heater element.
11. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal C and ground.

⇒	If less than specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the HSM.

⇒	If greater than specified range, test the signal circuit for an short to voltage. If the circuit tests normal, replace the HSM.

12. Ignition OFF, connect the harness connector at the seat cushion heater element and disconnect the harness connector at the HSM.
13. Test for 2.5-10 ohms between the supply voltage circuit terminal 8 and the ground circuit terminal 2.

⇒	If greater than the specified range, test the supply voltage circuit and the ground circuit for an open/high resistance. If the circuits test normal, test or replace the seat cushion heater element.

14. If all circuits test normal, replace the HSM.

Heated Seats Indicator Circuit Inoperative

1. Ignition OFF, disconnect the harness connector at the HSM.
2. Install a test lamp between the control circuit terminal 4 and the B+. Verify the heated seat high heat indicator is illuminated.

⇒	If the indicator does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

3. Install a test lamp between the control circuit terminal 1 and the B+. Verify the heated seat low heat indicator is illuminated.

⇒	If the indicator does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

4. If all circuits test normal, replace the HSM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.