For 1990-2009 cars

## DTC B1935 or B2180 With Memory A45

### 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 B1935 04: Left Seat Back Heater Circuit Open
DTC B1935 0A: Left Seat Back Heater Circuit Rate of Change Below Threshold
DTC B1935 0B: Left Seat Back Heater Circuit Current Above Threshold
DTC B1935 0C: Left Seat Back Heater Circuit Current Below Threshold
DTC B1935 0D: Left Seat Back Heater Circuit Resistance Above Threshold
DTC B1935 0E: Left Seat Back Heater Circuit Resistance Below Threshold
DTC B1935 1F: Left Seat Back Heater Circuit Intermittent
DTC B2180 04: Right Seat Back Heater Circuit Open
DTC B2180 0A: Right Seat Back Heater Circuit Rate of Change Below Threshold
DTC B2180 0B: Right Seat Back Heater Circuit Current Above Threshold
DTC B2180 0C: Right Seat Back Heater Circuit Current Below Threshold
DTC B2180 0D: Right Seat Back Heater Circuit Resistance Above Threshold
DTC B2180 0E: Right Seat Back Heater Circuit Resistance Below Threshold
DTC B2180 1F: Right Seat Back Heater Circuit Intermittent

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ MSM Terminal 5 X3 | 1, 2, B1935 0C, B1935 0D, B2180 0C, B2180 0D, B2425 0C, B2425 0D, B2430 0C, B2430 0D | 1, 2, B1935 0C, B1935 0D, B2180 0C, B2180 0D, B2425 0C, B2425 0D, B2430 0C, B2430 0D | -- | --
Driver Heated Seat Back Element Supply Voltage | B2508 02 | B1935 0C, B1935 0D | B2345 00, B2508 01 | B1935 0B, B1935 0E
Driver Heated Seat Back Element Control | B2345 00, B2508 02 | B1935 0C, B1935 0D | B2345 00, B2508 01 | B1935 0B, B1935 0E
Driver Heated Seat Back Temperature Sensor Signal | B2435 02 | B1935 04, B1935 1F, B2435 0D | B1935 04, B1935 1F, B2435 0D | B1935 0A, B2345 13, B2345 42, B2345 4B
Driver Heated Seat Back Temperature Sensor Low Reference | -- | B1935 04, B1935 1F, B2435 0D | -- | B2345 13, B2345 42, B2345 4B
Driver Heated Seat Cushion Element Supply Voltage | B2508 02 | B2425 0C, B2425 0D | B2345 00, B2508 01 | B2425 0B, B2425 0E
Driver Heated Seat Cushion Element Control | B2345 00, B2508 02 | B2425 0C, B2425 0D | B2345 00, B2508 01 | B2425 0B, B2425 0E
Driver Heated Seat Cushion Temperature Sensor Signal | B1925 02, B2425 1F | B1925 05, B2425 04, B2425 1F | B1925 05, B2425 04, B2425 1F | B2345 13, B2345 42, B2345 4B, B2425 0A
Driver Heated Seat Cushion Temperature Sensor Low Reference | -- | B1925 05, B2425 04, B2425 1F | -- | B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Back Element Supply Voltage | B2508 02 | B2180 0C, B2180 0D | B2345 00, B2508 01 | B2180 0B, B2180 0E
Passenger Heated Seat Back Element Control | B2345 00, B2508 02 | B2180 0C, B2180 0D | B2345 00, B2508 01 | B2180 0B, B2180 0E
Passenger Heated Seat Back Temperature Sensor Signal | B2440 02 | B2180 04, B2180 1F, B2440 05 | B2180 04, B2180 1F, B2440 05 | B2180 0A, B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Back Temperature Sensor Low Reference | -- | B2180 04, B2180 1F, B2440 05 | -- | B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Cushion Element Supply Voltage | B2508 02 | B2430 0C, B2430 0D | B2345 00, B2508 01 | B2430 0B, B2430 0E
Passenger Heated Seat Cushion Element Control | B2345 00, B2508 02 | B2430 0C, B2430 0D | B2345 00, B2508 01 | B2430 0B, B2430 0E
Passenger Heated Seat Cushion Temperature Sensor Signal | B2170 02, B2430 1F | B2430 04, B2430 1F, B2170 05 | B2430 04, B2430 1F, B2170 05 | B2345 13, B2345 42, B2345 4B, B2430 0A
Passenger Heated Seat Cushion Temperature Sensor Low Reference | -- | B2430 04, B2430 1F, B2170 05 | -- | B2345 13, B2345 42, B2345 4B
1. Power seat inoperative 2. Heated seat inoperative

### Circuit/System Description

The driver and front passenger heated seats are controlled by the memory seat module (MSM). When active, power is applied to the seat cushion and back heater elements through a common voltage supply circuit. Each individual heater element is grounded by the MSM through separate low side drive control circuits. The heater element control circuits are pulse width modulated to ground by the module in order to control the seat temperatures by regulating the current flow through the heater elements. The module then monitors the current flow through the heating elements and the of rate change of the temperature sensor to verify correct heated seat operation.

### Conditions for Running the DTC

The MSM must be powered.

### Conditions for Setting the DTC

The heated seat system must be active.

#### B1935 04, B2180 04

The MSM does not detect a temperature change for up to 210 seconds.

#### B1935 0A, B2180 0A

The MSM detects that the set point temperature has not been reached for up to 8.5 minutes.

#### B1935 0B, B1935 0E, B2180 0B, B2180 0E

By measuring the current and voltage output to the seat back heating element every 10 seconds, the MSM calculates that the heating element resistance is below the minimum resistance value of 3.5 ohms.

#### B1935 0C, B1935 0D, B2180 0C, B2180 0D

By measuring the current and voltage output to the seat back heating element every 10 seconds, the MSM calculates that the heating element resistance is above the maximum resistance value of 10 ohms.

#### B1935 1F, B2180 1F

The temperature sensor voltage is erratic or changes suddenly.

### Action Taken When the DTC Sets

The heated seat back function for the appropriate seat will be disabled.

### Conditions for Clearing the DTC

• | The current DTC clears when the malfunction is no longer present and the power mode changes to 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

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

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Testing

#### B1935 0A, B1935 0B, B1935 0C, B1935 0D, B1935 0E, B1935 04, or B1935 1F

1. Ignition OFF, disconnect the X3 harness connector at the MSM.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 5 and ground.

⇒ | 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 X3 harness connector at the MSM and disconnect the X1 harness connector at the MSM.

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

4. Test for 6-14.1 ohms between control circuit terminal 6 and control circuit terminal 1.

⇒ | If greater than the specified range, test the control circuits for an open/high resistance. If the circuits test normal, replace the seat back heating element.

⇒ | If less than the specified range, test for a short between the control circuits. If the circuits test normal, replace the seat back heating element.

5. Ignition OFF, disconnect the X2, X5 harness connectors at the MSM.
6. Test for 3.3K-300K ohms between the signal circuit terminal 4 X5 and the low reference circuit terminal 2 X2.

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

7. Ignition OFF, connect the X1, X2, X5 harness connectors at the MSM.
8. Disconnect the harness connector at the seat back heating element/temperature sensor.
9. 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 MSM.

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

10. If all circuits test normal, replace the MSM.

#### B2180 0A, B2180 0B, B2180 0C, B2180 0D, B2180 0E, B2180 04, or B2180 1F

1. Ignition OFF, disconnect the X3 harness connector at the MSM.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 5 and ground.

⇒ | 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 X3 harness connector at the MSM and disconnect the X1 harness connector at the MSM.

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

4. Test for 6-14.3 ohms between control circuit terminal 14 and control circuit terminal 4.

⇒ | If greater than the specified value, test the control circuits for an open/high resistance. If the circuits test normal, replace the seat back heating element.

⇒ | If less than the specified range, test for a short between the control circuits. If the circuits test normal, replace the seat back heating element.

5. Ignition OFF, disconnect the X2, X5 harness connectors at the MSM.
6. Test for 3.3K-300K ohms between the signal circuit terminal 3 X5 and the low reference circuit terminal 5 X2.

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

7. Ignition OFF, connect the X1, X2, X5 harness connectors at the MSM.
8. Disconnect the harness connector at the seat back heating element/temperature sensor.
9. 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 MSM.

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

10. If all circuits test normal, replace the MSM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Driver or Passenger Seat Back Cushion Heater Replacement

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

## DTC B1935 or B2180 Without Memory A45

### 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 B1935 04: Left Seat Back Heater Circuit Open
DTC B1935 0A: Left Seat Back Heater Circuit Rate of Change Below Threshold
DTC B1935 0B: Left Seat Back Heater Circuit Current Above Threshold
DTC B1935 0C: Left Seat Back Heater Circuit Current Below Threshold
DTC B1935 0D: Left Seat Back Heater Circuit Resistance Above Threshold
DTC B1935 0E: Left Seat Back Heater Circuit Resistance Below Threshold
DTC B1935 1F: Left Seat Back Heater Circuit Intermittent
DTC B2180 04: Right Seat Back Heater Circuit Open
DTC B2180 0A: Right Seat Back Heater Circuit Rate of Change Below Threshold
DTC B2180 0B: Right Seat Back Heater Circuit Current Above Threshold
DTC B2180 0C: Right Seat Back Heater Circuit Current Below Threshold
DTC B2180 0D: Right Seat Back Heater Circuit Resistance Above Threshold
DTC B2180 0E: Right Seat Back Heater Circuit Resistance Below Threshold
DTC B2180 1F: Right Seat Back Heater Circuit Intermittent

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Driver Heated Seat Back Element Supply Voltage | B2508 02 | B1935 0C, B1935 0D | B2345 00, B2508 01 | B1935 0B, B1935 0E
Driver Heated Seat Back Element Supply Control | B2345 00, B2508 02 | B1935 0C, B1935 0D | B2345 00, B2508 01 | B1935 0B, B1935 0E
Driver Heated Seat Back Temperature Sensor Signal | B2435 02 | B1935 04, B1935 1F, B2435 0D | B1935 04, B1935 1F, B2435 0D | B1935 0A, B2345 13, B2345 42, B2345 4B
Driver Heated Seat Back Temperature Sensor Low Reference | -- | B1935 04, B1935 1F, B2435 0D | -- | B2345 13, B2345 42, B2345 4B
Driver Heated Seat Cushion Element Supply Voltage | B2508 02 | B2425 0C, B2425 0D | B2345 00, B2508 01 | B2425 0B, B2425 0E
Driver Heated Seat Cushion Element Control | B2345 00, B2508 02 | B2425 0C, B2425 0D | B2345 00, B2508 01 | B2425 0B, B2425 0E
Driver Heated Seat Cushion Temperature Sensor Signal | B1925 02, B2425 1F | B1925 05, B2425 04, B2425 1F | B1925 05, B2425 04, B2425 1F | B2345 13, B2345 42, B2345 4B, B2425 0A
Driver Heated Seat Cushion Temperature Sensor Low Reference | -- | B1925 05, B2425 04, B2425 1F | -- | B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Back Element Supply Voltage | B2508 02 | B2180 0C, B2180 0D | B2345 00, B2508 01 | B2180 0B, B2180 0E
Passenger Heated Seat Back Element Control | B2345 00, B2508 02 | B2180 0C, B2180 0D | B2345 00, B2508 01 | B2180 0B, B2180 0E
Passenger Heated Seat Back Temperature Sensor Signal | B2440 02 | B2180 04, B2180 1F, B2440 05 | B2180 04, B2180 1F, B2440 05 | B2180 0A, B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Back Temperature Sensor Low Reference | -- | B2180 04, B2180 1F, B2440 05 | -- | B2345 13, B2345 42, B2345 4B
Passenger Heated Seat Cushion Element Supply Voltage | B2508 02 | B2430 0C, B2430 0D | B2345 00, B2508 01 | B2430 0B, B2430 0E
Passenger Heated Seat Cushion Element Control | B2345 00, B2508 02 | B2430 0C, B2430 0D | B2345 00, B2508 01 | B2430 0B, B2430 0E
Passenger Heated Seat Cushion Temperature Sensor Signal | B2170 02, B2430 1F | B2430 04, B2430 1F, B2170 05 | B2430 04, B2430 1F, B2170 05 | B2345 13, B2345 42, B2345 4B, B2430 0A
Passenger Heated Seat Cushion Temperature Sensor Low Reference | -- | B2430 04, B2430 1F, B2170 05 | -- | B2345 13, B2345 42, B2345 4B

### Circuit/System Description

The left and right heated seats are controlled by the heated seat module (HSM). When active, power is applied to the seat cushion and back heater elements through a common voltage supply circuit. Each individual heater element is grounded by the HSM through separate low side drive control circuits. The heater element control circuits are pulse width modulated to ground by the module in order to control the seat temperature by regulating the current flow through the heater elements. The module then monitors the current flow through the heating elements and the of rate change of the temperature sensors to verify correct heated seat operation.

### Conditions for Running the DTC

The HSM must be powered.

### Conditions for Setting the DTC

The heated seat system must be active.

#### B1935 04, B2180 04

The HSM does not detect a temperature change for up to 210 seconds.

#### B1935 0A, B2180 0A

The HSM detects that the set point temperature has not been reached for up to 8.5 minutes.

#### B1935 0B, B1935 0E, B2180 0B, B2180 0E

By measuring the current and voltage output to the seat back heating element every 10 seconds, the HSM calculates that the heating element resistance is below the minimum resistance value of 3.5 ohms.

#### B1935 0C, B1935 0D, B2180 0C, B2180 0D

By measuring the current and voltage output to the seat back heating element every 10 seconds, the HSM calculates that the heating element resistance is above the maximum resistance value of 10 ohms.

#### B1935 1F, B2180 1F

The temperature sensor voltage is erratic or changes suddenly.

### Action Taken When the DTC Sets

The heated seat back function for the appropriate seat will be disabled.

### Conditions for Clearing the DTC

• | The current DTC clears when the malfunction is no longer present and the power mode changes to 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

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

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Testing

#### B1935 0A, B1935 0B, B1935 0C, B1935 0D, B1935 0E, B1935 04, or B1935 1F

1. Ignition OFF, disconnect the X1 harness connector 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 6.0-14.1 ohms between the control circuit terminal 3 and the control circuit terminal 1.

⇒ | If greater than the specified range, test the control circuits for an open/high resistance. If the circuits test normal, replace the seat back heating element/temperature sensor.

⇒ | If less than the specified range, test for a short between the control circuits. If the circuits test normal, replace the seat back heating element/temperature sensor.

3. Ignition OFF, disconnect the X2, X4 harness connectors at the HSM.
4. Test for 3.3K-300K ohms between the signal circuit terminal 19 X4 and the low reference circuit terminal 5 X2.

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

5. Ignition OFF, connect the X1, X2, X4 harness connectors at the HSM.
6. Disconnect the harness connector at the seat back heating element/temperature sensor.
7. 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 voltage. If the circuit tests normal, replace the HSM.

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

#### B2180 0A, B2180 0B, B2180 0C, B2180 0D, B2180 0E, B2180 04, or B2180 1F

1. Ignition OFF, disconnect the X1 harness connector 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 6.0-14.3 ohms between the control circuit terminal 6 and the control circuit terminal 4.

⇒ | If greater than the specified value, test the control circuits for an open/high resistance. If the circuits test normal, replace the seat back heating element/temperature sensor.

⇒ | If less than the specified range, test for a short between the control circuits. If the circuits test normal, replace the seat back heating element/temperature sensor.

3. Ignition OFF, disconnect the X2, X4 harness connectors at the HSM.
4. Test for 3.3K-300K ohms between the signal circuit terminal 10 X4 and the low reference circuit terminal 7 X2.

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

5. Ignition OFF, connect the X1, X2, X4 harness connectors at the HSM.
6. Disconnect the harness connector at the seat back heating element/temperature sensor.
7. 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 voltage. If the circuit tests normal, replace the HSM.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Driver or Passenger Seat Back Cushion Heater Replacement

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