Operation CHARM: Car repair manuals for everyone.
Home >> Buick >> 2009 >> LaCrosse V6-3.8L >> Repair and Diagnosis >> Body and Frame >> Seats >> Seat Temperature Element >> Testing and Inspection >> Symptom Related Diagnostic Procedures >> Front Heated Seat Malfunction

Front Heated Seat Malfunction




Front Heated Seat Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

The driver and passenger heated seats are controlled by separate heated seat switches located in the HVAC control module. When a heated seat switch is pressed, the HVAC control module sends a serial data message to the body control module (BCM) indicating the heated seat command. In response to this signal, the BCM applies battery positive voltage through the heated seat relay control circuit energizing the relay coil. The relay closes its switch contacts applying battery positive voltage through the element supply voltage circuit to the seat heating elements. The BCM then sends a serial data message back to the HVAC control module to illuminate the appropriate temperature indicator.

Reference Information
Schematic Reference

Heated/Cooled Seat Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Heated Seats Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)

Circuit/System Verification

1. Ignition ON, observe the scan tool Driver Heated Seat parameter while pressing the driver heated seat switch from off to the high and low heat positions. The reading should change between Off, High, and Low.

• If the reading does not change between the specified values and no current or history DTCs are set, replace the HVAC control module.

2. Ignition ON, observe the scan tool Passenger Heated Seat parameter while pressing the passenger heated seat switch from off to the high and low heat positions. The reading should change between Off, High, and Low.

• If the reading does not change between the specified values, replace the HVAC control module.

3. If all scan tool parameters test normal, refer to Circuit/System Testing.
4. If all scan tool parameters test normal, the heated seat operates normal, but the heated seat switch temperature indicators are inoperative or always ON, replace the HVAC control module.

Circuit/System Testing

1. Ignition OFF, disconnect the appropriate heated seat relay.
2. Test for less than 5.0 Ohms between the ground circuit terminal C2 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A2 and ground.

• 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.

4. Verify that a test lamp does not illuminate between the control circuit terminal C1 and ground.

• If the test lamp illuminates, test the control circuit for a short to voltage.

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.

• 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 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 Ohms between the ground circuit terminal B and ground.

• 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 Ohms between terminal A and terminal B.

• 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 1-5 Ohms between terminal A and terminal D.

• If not within the specified range, replace the seat cushion heater element.

12. Connect the harness connectors at the seat back and seat cushion heater elements.
13. Connect a 10 A fused jumper wire between the B+ circuit terminal A2 and the control circuit terminal C1. The seat should get warm.

• If the seat does not get warm, test the control circuit and the circuit between the seat heater elements for an open/high resistance.

14. 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 Ohms between terminal A and terminal D.

• If not within the specified range, replace the seat cushion heater element.

3. Test for 535-168k Ohms between terminal B and terminal C.

• 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 Ohms between terminal A and terminal B.

• 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 Ohms between terminals 85 and 86.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the terminals listed below:

* 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 Ohms between terminals 30 and 87.

• If greater than the specified range, replace the heated seat relay.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Driver or Passenger Seat Back Cushion Heater Replacement (Driver or Passenger Seat Back Cushion Heater Replacement)
* Driver or Passenger Seat Cushion Heater Replacement (Driver or Passenger Seat Cushion Heater Replacement)
* Control Module References (Programming and Relearning) for BCM and HVAC control module replacement, setup, and programming

pro multis · About Operation CHARM