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 B1925: Left Front Seat Heater Sensor

DTC B2170: Right Front Passenger Seat Heater Sensor

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Heated Seat Relay B+

1, B1920, B2165

1, B1920, B2165

--

--

Heated Seat Relay Control

1, B2508, B2509

B2508, B2509

B2508, B2509

--

Heated Seat Relay Ground

--

B2508, B2509

--

--

Heated Seat Cushion Temperature Sensor Signal

B1925, B2170

B1920, B2165

B1920, B1925, B2165, B2170

--

Heated Seat Cushion Temperature Sensor Low Reference

--

1, B1920, B2165

--

--

Heated Seat Heater Element Control

1, B1920, B2165

1, B1920, B2165

--

--

Heated Seat Element Ground

--

1, B1920, B2165

--

--

1. Front heated seat malfunction

Circuit/System Description

The heated seat temperature sensor is located in the seat cushion just under the seat cover within the seat heating element. The body control module (BCM) supplies the heated seat temperature sensor with a temperature sensor signal circuit and a temperature sensor low reference circuit. The BCM monitors the voltage of the heated seat temperature sensor signal circuit to determine the temperature of the seat. The BCM cycles the heated seat relay on and off in order to maintain the desired seat temperature based on the voltage feedback from the temperature sensor.

The BCM also monitors the sensor signal circuit for a change in voltage that is either to fast or to slow. The slow rate check is performed only when the heated seat is initially turned on with a cold seat in order to prevent setting a false DTC.

Conditions for Running the DTC

    • DTC B1327 must not be present.
    • Battery voltage must be between 9-16 V.

Conditions for Setting the DTC

B1925

The DTC will set when the BCM detects a short to ground or voltage in the driver temperature sensor signal circuit.

B2170

The DTC will set when the BCM detects a short to ground or voltage in the passenger temperature sensor signal circuit.

Actions Taken When the DTC Sets

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

Conditions for Clearing the DTC

    • The current DTC will clear and set to history 3 seconds after the reference voltage returns to the normal operating range.
    • The condition responsible for setting the DTC no longer exists.
    • A history DTC will clear once 50 consecutive fault-free ignition cycles have occurred.

Diagnostic Aids

When DTC B1925 or B2170 are set as current, the BCM disables the heated seat function not allowing any heated seat relay control functions to occur. Cycling the ignition OFF then ON will reset the DTC and allow relay commands.

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

  1. Ignition OFF, disconnect the appropriate heated seat cushion heater element.
  2. Test for less than 5.0 Ω between the low reference circuit terminal C 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 BCM.
  4. Ignition ON, test for 9.8-10.2 V between the signal circuit terminal D and ground.
  5. 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 BCM.
    If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  6. If all circuits test normal, test or replace the seat cushion heater element.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Driver or Passenger Seat Cushion Heater Replacement
    •  Control Module References for BCM replacement, setup, and programming