When the ignition is ON and the heated steering wheel switch is pressed, the switch circuit is pulled to ground. The heat module monitors the switch circuit, and turns the steering wheel heat system ON or OFF when the circuit is grounded. The heat module supplies voltage to the indicator lamp when the system is on. The heat module monitors the resistance of the thermistor, and supplies voltage to the heat elements when the temperature of the steering wheel is not above its normal operating range.

The resistance of the thermistor and the heat elements will vary with the temperature of the steering wheel.

Schematic Reference:

Connector End View Reference:

Steering Wheel and Column Connector End Views

Description and Operation:

Steering Wheel and Column Description and Operation

Electrical Information Reference:

1. Ignition ON, press and release the heated steering wheel switch, located on the left side of the steering wheel. Observe that the heated steering wheel indicator illuminates, and feel the left and right sides of the steering wheel become warm.
2. Press and release the heated steering wheel switch again. Observe that the indicator turns OFF.

1. Ignition OFF, disable the SIR system and remove the inflatable restraint module from the steering wheel.
2. Remove and disconnect the heat control module, located at the top of the steering wheel.
3. Ignition ON, measure resistance between ground circuit terminal 1 and ground.

⇒	If greater than 1.0 ohm, repair the open or high resistance in the ground circuit.

4. Test for battery voltage on the ignition 1 voltage circuit terminal 4 of the heat control module connector.

⇒	If battery voltage is not present, test for and repair the open in the ignition 1 voltage circuit.

5. Measure voltage between the ignition voltage circuit terminal 4 and the switch circuit terminal 7. Press and release the heated steering wheel switch. Verify that there is battery voltage between terminals 4 and 7 when the switch is pressed, and no voltage when the switch is released.

⇒	If there is no voltage when the switch is pressed, test the switch circuit for an open. If the circuit tests normal, test or replace the switch.

6. Connect a 3 A fused jumper between the indicator control circuit terminal 3 and the ignition voltage circuit terminal 4. Verify that the heated wheel indicator illuminates when terminals 3 and 4 are jumpered together.

⇒	If the indicator does not illuminate when terminals 3 and 4 are jumpered, test the indicator control circuit for an open, short to ground, or high resistance. If the circuit tests normal, test or replace the switch.

7. Test for 6K - 35K ohms of resistance between the thermistor circuit terminal 5 and ground.

⇒	If not within the specified range, test the thermistor circuit for an open/high resistance. If the circuit tests normal, test or replace the steering wheel.

8. Test for 0.6 - 5.0 ohms of resistance between the heater element circuit terminal 6 and ground.

⇒	If not within the specified range, test the heater element circuit for an open/high resistance. If the circuit tests normal, test or replace the steering wheel.

9. If all circuits test normal, replace the steering wheel heat control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.