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.

### DTC Descriptors

DTC B1925 02: Left Seat Heater Sensor Circuit Short to Ground
DTC B1925 05: Left Seat Heater Sensor Circuit Short to Battery or Open
DTC B2170 02: Right Seat Heater Cushion Sensor Circuit Short to Ground
DTC B2170 05: Right Seat Heater Cushion Sensor Circuit Short to Battery or Open

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Driver Heated Seat Element Supply Voltage | B2345 00, B2508 02 | B2425 0C, B2425 0D | B2345 00, B2508 01 | --
Driver Heated Seat Element Control | B2345 00, B2508 02 | B2425 0C, B2425 0D | B2345 00, B2508 01 | --
Driver Heated Seat Temperature Sensor Signal | B1925 02 | B1925 05, B2425 04, B2425 1F | B1925 05, B2425 04, B2425 1F | B2345 13, B2345 42, B2345 4B
Driver Heated Seat Temperature Sensor Low Reference | -- | B1925 05, B2425 04, B2425 1F | -- | B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Element Supply Voltage | B2345 00, B2508 02 | B2430 0C, B2430 0D | B2345 00, B2508 01 | --
Passenger Heated Seat Element Control | B2345 00, B2508 02 | B2430 0C, B2430 0D | B2345 00, B2508 01 | --
Passenger Heated Seat Temperature Sensor Signal | B2170 02 | B2170 05, B2430 04, B2430 1F | B2170 05, B2430 04, B2430 1F | B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Temperature Sensor Low Reference | -- | B2170 05, B2430 04, B2430 1F | -- | B2345 13, B2345 42, B2345 4B

### Circuit/System Description

The heated seat temperature sensor that set this diagnostic trouble code (DTC) is located in the seat cushion just under the seat cover with the seat heating element. The heated seat module (HSM) supplies a 5-volt reference voltage through the temperature sensor signal circuit and a ground through the low reference circuit to the sensor. The HSM monitors the voltage of the sensor signal circuit to determine the temperature of the seat. The temperature sensor varies in resistance based on the temperature of the heating element causing the signal voltage to change. Once the seat reaches the switch set temperature, the HSM will then cycle the control circuit of the heating elements ON and OFF in order to maintain the desired seat temperature based on the feedback voltage from the sensor.

### Conditions for Running the DTC

The HSM must be powered.

### Conditions for Setting the DTC

#### B1925 02, B2170 02

The temperature sensor voltage drops below 0.8 volt for more than 1 second.

#### B1925 05, B2170 05

The temperature sensor voltage is greater than 5 volts for more than 1 second.

### Action Taken When the DTC Sets

The heated seat function for the affected seat will be disabled.

### Conditions for Clearing the DTC

• | The current DTC will clear and set the code to history 3 seconds after the reference voltage returns to normal operating range and the ignition is cycled OFF then back to ACC or RUN.

• | The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred.

### Reference Information

#### Schematic Reference

Heated/Cooled Seat Schematics

#### Connector End View Reference

Heated/Cooled Seat Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Testing

#### B1925 02 or B1925 05

1. Ignition OFF, disconnect the C2, C4 harness connectors at the HSM.

Important: When measuring the resistance, the resistance values are based on the seat being at room temperature of 20°C (68°F).

2. Test for 1.9K-300K ohms between the signal circuit terminal 9 C4 and the low reference circuit terminal 6 C2.

⇒ | If greater than the specified range, test the signal circuit and the low reference 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 and low reference circuits. If the circuits test normal, replace the seat temperature sensor.

3. Ignition OFF, connect the C2, C4 harness connectors to the HSM.
4. Disconnect the harness connector at the seat cushion heating element/temperature sensor.
5. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal C and ground.

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

⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the HSM.

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

#### B2170 02 or B2170 05

1. Ignition OFF, disconnect the C2, C4 harness connectors at the HSM.

Important: When measuring the resistance, the resistance values are based on the seat being at room temperature of 20°C (68°F).

2. Test for 1.9K-30K ohms between the signal circuit terminal 20 C4 and the low reference circuit terminal 8 C2.

⇒ | If greater than the specified range, test the signal circuit and the low reference 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 and low reference circuits. If the circuits test normal, replace the seat temperature sensor.

3. Ignition OFF, connect the C2, C4 harness connectors to the HSM.
4. Disconnect the harness connector at the seat cushion heating element/temperature sensor.
5. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal C and ground.

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

⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the HSM.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Driver or Passenger Seat Cushion Heater Replacement

• | Control Module References for HSM replacement, setup, and programming