For 1990-2009 cars

### Diagnostic Instructions

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

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ Heated Seat Switch | 1 | 1 | -- | --
B+ Heated Seat Module | 1 | 1 | -- | --
Heated Seat Element Supply Voltage | 1 | 1 | 3 | --
Heated Seat High/Low Signal | 1 | 1 | -- | --
Heated Seat Switch Signal | 1 | 1 | -- | --
Heated Seat Temperature Signal | 1 | 1 | 1 | 1
Ground - Heated Seat Module | -- | 1 | -- | --
Ground - Heated Seat Element | -- | 1 | -- | --
Ground - Heated Seat Switch Indicator | -- | 2 | 2 | --
1. Heated seat inoperative 2. Heated seat indicators inoperative 3. Heated seat always on

### Circuit/System Description

Battery positive voltage is supplied at all times to the heated seat module through the battery positive voltage circuit and the heated seat fuse located in the rear fuse block. When commanded ON, the heated seat module uses this voltage to heat the seat heating elements. The heated seat module and the seat heating elements are grounded through the module ground circuit to G305.

When the heated seat switch is placed in either the high, medium, or low temperature position, a PWM signal is applied through the heated seat switch signal circuit to the heated seat module. In response to this signal, the module applies battery positive voltage through the heated seat element supply voltage circuit to the seat heating elements. The heated seat module supplies a 5-volt reference voltage through the temperature sensor signal circuit and a low reference to the heated seat temperature sensor (thermistor) that is located under the cover of the seat cushion. The heated seat module monitors this reference voltage to determine the temperature of the seat. Once the seat reaches the heated seat switch set temperature, the module will then cycle the heating element supply voltage ON and OFF in order to maintain the desired seat temperature.

### Reference Information

#### Schematic Reference

Heated/Cooled Seat Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Heated Seats Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Verification

1. Ignition ON, cycle the heated seat switch through the high, medium, and low positions. The heated seats should operate in all three modes.

⇒ | If the heated seat does not operate, refer to Heated Seats Inoperative.

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

⇒ | If one or more of the indicators do not illuminate, refer to Headed Seat Indicator Inoperative.

### Circuit/System Testing

#### Heated Seats Inoperative

1. Ignition OFF, disconnect the harness connector at the hazard warning and accessory switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuits listed below and ground:

• | B+ terminal 12

• | B+ terminal 13

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

3. Ignition OFF, connect the harness connector at the hazard warning and accessory switch and disconnect the harness connector at the appropriate seat.
4. Test for less than 1 ohm between the ground circuit terminal 9 and ground.

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

5. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 8 and ground.

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

6. Place the heated seat switch in the HIGH heat position and test for approximately 10 volts between the signal circuit terminal 7 and ground.

⇒ | If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the hazard warning and accessory switch.

7. Place the heated seat switch in the MEDIUM heat position and test for approximately 7 volts between the signal circuit terminal 7 and ground.

⇒ | If not the specified value, test or replace the hazard warning and accessory switch.

8. Place the heated seat switch in the LOW heat position and test for approximately 1.0 volts between the signal circuit terminal 7 and ground.

⇒ | If not the specified value, test or replace the hazard warning and accessory switch.

9. Ignition OFF, disconnect the harness connector at the seat back cushion heater element.
10. At the cushion side of the harness connector, test for 0.5-5 ohms between the control circuit terminal 1 and the ground circuit terminal 2.

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

11. If all circuits test normal, replace the seat cushion heater element/module.

#### Heated Seats Indicator Circuit Inoperative

1. Ignition OFF, disconnect the harness connector at the appropriate heated seat switch.
2. Test for less than 1 ohm between the ground circuit terminal 2 and ground.

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

3. If all circuits test normal, test or replace the hazard warning and accessory switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Front Seat Heater Switch Replacement

• | Driver or Passenger Seat Back Cushion Heater Replacement

• | Driver or Passenger Seat Cushion Heater Replacement