GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 DTS 🢒 Seats 🢒 Seat Heating and Cooling 🢒 Heated Seat Inoperative - Rear

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.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Heated Seat Switch Ground

1

1

--

--

Heated Seat Switch Indicator Supply Voltage

3

3

--

--

Heated Seat Back Only Indicator Control

4

3

3

--

Heated Seat Back Only Mode Switch Signal

2

2

2

--

Heated Seat Back/Cushion Indicator Control

4

3

3

--

Heated Seat Low Temperature Indicator Control

4

3

3

--

Heated Seat Medium Temperature Indicator Control

4

3

3

--

Heated Seat High Temperature Indicator Control

4

3

3

--

Heated Seat Temperature Switch Signal

1

1

1

--

1. Heated seat inoperative

2. Heated seat back only mode inoperative

3. Heated seat switch indicator inoperative

4. Heated seat switch indicator always on

Circuit/System Description

The left and right rear passenger heated seats are controlled by separate heated seat switches. The switches are located on the rear door panels. When a heated seat switch is pressed, ground is momentarily applied through the switch contacts and the switch signal circuit to the rear heated seat module (RHSM). In response to this signal, the RHSM applies battery voltage through the element supply voltage circuits to the seat cushion and seat back heating elements. The RHSM then supplies a ground through the appropriate indicator control circuits to the heated seat switch illuminating the appropriate switch indicators.

Reference Information

Schematic Reference

Heated/Cooled Seat Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Rear 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
  1. Ignition ON, observe the appropriate scan tool Rear Heated Seat Module Rear Seat HVC Mode parameter while pressing the heated seat back/cushion mode switch. The reading should change between Off and Back and Cushion.
    2. ⇒If not Back and Cushion, refer to Circuit/System Testing.
  2. Observe the appropriate scan tool Rear Seat HVC Mode parameter while pressing the heated seat back only mode switch. The reading should change between Back and Cushion and Back Only.
    3. ⇒If not Back Only, refer to Circuit/System Testing.
  3. If all scan tool parameters test normal and there are no DTCs set, replace the RHSM.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the appropriate heated seat switch.
  2. Test for less than 5 ohms between the ground circuit terminal J and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, observe the appropriate scan tool Rear Seat HVC Mode parameter. The reading should be Off.
    4. ⇒If not the specified value, test the signal circuits terminal A and terminal G for a short to ground. If the circuits tests normal, replace the RHSM.
  4. Install a 3A fused jumper wire between the signal circuit terminal G and ground. Verify the scan tool Rear Seat HVC Mode parameter reading is Back and Cushion.
    5. ⇒If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the RHSM.
  5. Install a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool Rear Seat HVC Mode parameter reading is Back Only.
    6. ⇒If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the RHSM.
  6. If all circuits tests normal, test or replace the heated seat switch.

Component Testing

Rear Heated Seat Switch

  1. Ignition OFF, disconnect the harness connector at the heated seat switch switch.
  2. Test for infinite resistance between the signal terminal G and the ground terminal J with the seat back and cushion switch in the open position.
    3. ⇒If not the specified value, replace the heated seat switch switch.
  3. Test for infinite resistance between the signal terminal A and the ground terminal J with the seat back only switch in the open position.
    4. ⇒If not the specified value, replace the heated seat switch switch.
  4. Test for less than 5 ohms between the signal terminal G and the ground terminal J with the seat back and cushion switch in the closed position.
    5. ⇒If greater than the specified range, replace the heated seat switch.
  5. Test for less than 5 ohms between the signal terminal A and the ground terminal J with the seat back only switch in the closed position.
    6. ⇒If greater than the specified range, replace the heated seat switch.
  6. Connect a 3A fused jumper wire between the B+ terminal K and battery voltage.
  7. Connect a test lamp between the following indicator control circuits and ground. The selected indicator should illuminate.
    8. • Seat back only mode indicator terminal B
    • Low heat indicator terminal C
    • Medium heat indicator terminal D
    • High heat indicator terminal E
    • Seat back cushion mode indicator terminal H
         ⇒If any indicator does not illuminate, replace the rear heated seat switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Rear Seat Heater Switch Replacement
    •  Control Module References for RHSM replacement, setup, and programming