GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 LaCrosse 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B1920 or B2165

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 B1920: Driver Seat Heater Timer Circuit

DTC B2165: Front Passenger Seat Heater Timer Circuit

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 signal circuit and a low reference circuit. The BCM monitors the voltage of the 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 volts.

Conditions for Setting the DTC

B1920

The DTC will set when the BCM detects that the change in voltage of the driver temperature sensor signal circuit is either to slow or to fast.

B2165

The DTC will set when the BCM detects that the change in voltage of the passenger temperature sensor signal circuit is either to slow or to fast.

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 B1920 or B2165 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.
    • Due to the nature of DTC B1920 and B2165, it may take up to 10 minutes for the DTCs to set. For purposes of testing in this diagnostic procedure the DTCs must be cleared or inactive.
    • Faults to other heated seat system circuits other than the temperature sensor signal circuit may also cause DTC B1920 and B2165 to set.

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 relay.
  2. Ignition OFF, test for less than 5.0 Ω between the ground circuit terminal C2 and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal C1 and ground.
    4. ⇒If the test lamp illuminates, test the control circuit for a short to voltage.
  4. Verify that a test lamp illuminates between the B+ circuit terminal A2 and ground.
    5. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal C1 for a short to ground.
  5. Connect a test lamp between the control circuit terminal A1 and ground.
  6. Command the appropriate Driver or Passenger Heated Seat ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    7. ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  7. Ignition OFF, disconnect the harness connector at the seat back heater element.
  8. Test for less than 5.0 Ω between the ground circuit terminal B and ground.
    9. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  9. At the heater element side of the connector, test for 1-5 Ω between the terminal A and Terminal B.
    10. ⇒If not within the specified range, replace the seat back heater element.
  10. Disconnect the harness connector at the seat cushion heater element.
  11. Test for less than 5 Ω between the low reference circuit terminal C and ground.
    12. ⇒If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
  12. Ignition ON, test for 9.8-10.2 volts between the signal circuit terminal B and ground.
    13. ⇒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.
  13. At the seat cushion side of the connector, test for 1-5 Ω between terminal A and terminal D.
    14. ⇒If not within the specified range, replace the seat cushion heater element.
  14. Test for 535-168k Ω between terminal B and terminal C.
    15. ⇒If not within the specified range, replace the seat cushion heater element.
  15. Connect the harness connectors at the seat back and seat cushion heater elements.
  16. Connect a 10 A fused jumper wire between the B+ circuit terminal A2 and the control circuit terminal C1. The seat should get warm.
    17. ⇒If the seat does not get warm, test the control circuit and the circuit between the seat heater elements for a short to ground or an open/high resistance.
  17. If all circuits test normal, test or replace the heated seat relay.

Component Testing

Seat Heater Elements

  1. Ignition OFF, disconnect the harness connector at the seat cushion heater element.
  2. Test for 1-5 Ω between terminal A and terminal D.
    3. ⇒If not within the specified range, replace the seat cushion heater element.
  3. Test for 535-168k Ω between terminal B and terminal C.
    4. ⇒If not within the specified range, replace the seat cushion heater element.
  4. Disconnect the harness connector at the seat back heater element.
  5. Test for 1-5 Ω between terminal A and terminal B.
    6. ⇒If not within the specified range, replace the seat back heater element.

Relay Test

  1. Ignition OFF, disconnect the appropriate heated seat relay.
  2. Test for 70-100 Ω between terminals 85 and 86.
    3. ⇒If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the terminals listed below:
    4. • 30 and 85
    • 30 and 86
    • 30 and 87
    • 85 and 87
    ⇒If not the specified value, replace the heated seat relay.
  4. Install a 10 A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.
    5. ⇒If greater than the specified range, replace the heated seat relay.

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