GM Service Manual Online
For 1990-2009 cars only

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 B2435: Driver Seat Back Heater Sensor Circuit

DTC B2440: Passenger Seat Back Heater Sensor Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Driver Heated Seat Sensor Signal

B2435

B2435

B2435

--

Passenger Heated Seat Sensor Signal

B2440

B2440

B2440

--

Driver Heated Seat Sensor Low Reference

B2435

B2435

B2435

--

Passenger Heated Seat Sensor Low Reference

B2440

B2440

B2440

--

Driver Seat Back Element Voltage Control

B2425

1

B2425

--

Driver Seat Cushion Element Voltage Control

B2425

1

B2425

--

Driver Seat Back and Cushion Element Low Reference Control

B2425

1

B2425

--

Passenger Seat Back Element Voltage Control

B2430

2

B2430

--

Passenger Seat Cushion Element Voltage Control

B2430

2

B2430

--

Passenger Seat Back and Cushion Element Low Reference Control

B2430

2

B2430

--

1. Driver heated seat inoperative.

2. Passenger heated seat inoperative.

Circuit/System Description

The heated seat temperature sensor that set this DTC is located in seat back just under the seat cover with the seat heating element. The memory seat module (MSM) supplies a separate 5-volt reference voltage through the temperature sensor signal circuit and a ground through the low reference circuit to the sensor. The MSM monitors the voltage of the sensor signal circuits 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 set temperature, the MSM will cycle the control circuits of the heating elements ON and OFF in order to maintain the desired seat temperature based on the feedback voltage from the sensors.

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

    • The heated seat sensor signal circuit voltage to the seat module is greater than 4.94 volts for 30 seconds or more.
    • The heated seat sensor signal circuit voltage to the seat module is less than 0.07 volt for 30 seconds or more.
    • The heated seat sensor signal circuit input to the seat module indicates that the desired seat temperature has not been reached within 34 minutes after activation.

Action Taken When the DTC Sets

The heated seat with a current status DTC will be disabled.

Conditions for Clearing the DTC

    • This DTC will clear on current status after the condition for setting the fault is corrected.
    • The history DTC will clear after 100 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 Verification

Ignition ON, observe the scan tool heated seat sensor parameters listed below. The readings should be between 4.94 and 0.07 volts and change from high to low as the seat gets warm.

    • Drvr. Seat Heat Sensor
    • Psgr. Seat Heat Sensor

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the appropriate seat back heater element.
  2. Test for less than 5.0 ohms between the low reference circuit terminal D and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the MSM.
  4. Ignition ON, verify the appropriate scan tool Seat Heat Sensor parameter is greater than 4.5 volts.
  5. If less than the specified range, test the signal circuit terminal C for a short to ground. If the circuit tests normal, replace the MSM.
  6. Install a 3A fused jumper wire between the signal circuit terminal C and the low reference circuit terminal D. Verify the scan tool Seat Heat Sensor parameter is less than 0.5 volts.
  7. If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the MSM.
  8. If all circuits test normal, test or replace the seat back heater element.

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, programming, and setup