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Home >> Cadillac >> 2008 >> STS AWD V6-3.6L >> 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.



Circuit/System Description

Battery positive voltage is supplied to the climate control seat module from the IGN 3 fuse located in the left rear fuse block. This voltage is used to power up the climate control seat module allowing the heated seats to operate only when the ignition switch is in the ON position. Battery positive voltage is also supplied at all times to the climate control seat module from the RF HTD ST/S-BAND fuse located in the right rear fuse block. This voltage is used by the module to supply power to the seat heating elements and is wired directly to the front passenger vented seat blower motors. Battery positive voltage is supplied directly to the driver vented seat blower motors from the DPM fuse located in the left rear fuse block. Ground is provided to the module at ground G307.


Diagnostic Aids

When performing resistance measurements on the heated seat system, make sure the seats are cooled. If the seat heating elements are still warm, resistance readings may be affected.


Reference Information
Schematic Reference

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

Component Connector End Views (Connector Views)
Description and Operation

Heated/Vented Seat Description and Operation (Heated/Vented Seat 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) for Scan Tool Information


Circuit System Verification

1. Ignition ON, with a scan tool, observe the following heated seat switch parameters while pressing and releasing the related switch. The readings should change between ACTIVE and INACTIVE as each switch is operated.

* Driver Heated Seat Sw.
* Pass. Heated Seat Sw.


• If the readings do not change as each switch is activated, replace the HVAC control module.

2. Ignition ON, operate both driver and front passenger heated seat functions. Both driver and front passenger heated seats should heat when commanded.

• If both driver and front passenger heated seats are inoperative, refer to Driver and Front Passenger Heated Seats Malfunction.
• If the driver heated seat is inoperative, refer to Driver Heated Seat Malfunction.
• If the front passenger heated seat is inoperative, refer to Front Passenger Heated Seat Malfunction.




Circuit/System Testing


Driver and Front Passenger Heated Seats Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the CCSM.
2. Ignition OFF, test for less than 5 ohms between the ground circuit terminal 6 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 ignition 3 B+ circuit terminal 3 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. Ignition OFF, disconnect the X1 harness connector at the CCSM.
5. Verify that a test lamp illuminates between the B+ circuit terminal B and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

6. Connect the X1 and X2 harness connectors at the CCSM.
7. Disconnect the harness connectors at the driver and front passenger cushion heated seat elements.
8. Verify that a test lamp illuminates between B+ and the temperature sensor low reference circuit terminal d.

• If the test lamp does not illuminate, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the CCSM.

9. If all circuits test normal, replace the CCSM.



Driver Heated Seat Malfunction
1. Ignition OFF, disconnect the X4 harness connector at the MSM.
2. Ignition ON, test for 4.50-5.50 volts between the PWM serial data circuit terminal 1 and ground.

• If less than the specified range, test the serial data circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CCSM.
• If greater than the specified range, test the serial data circuit for a short to voltage. If the circuit tests normal, replace the CCSM.

3. Ignition OFF, connect the X4 harness connector at the MSM.
4. Disconnect the harness connector at the driver cushion heated seat element.
5. Ignition OFF, test for less than 5 ohms between the cushion heater element ground circuit terminal B and ground.

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

6. Test for less than 5 ohms between the cushion heater element terminal A and terminal B at the cushion element.

• If greater than the specified range, replace the driver cushion heated seat element.

7. Test for 850-11.50K ohms between the cushion temperature sensor terminal C and terminal D.

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

8. Disconnect the harness connector at the driver back heated seat element.
9. Ignition OFF, test for less than 5 ohms between the back heater element ground circuit terminal B and ground.

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

10. Test for less than 5 ohms between the seat back heater element terminal A and terminal B at the seat back element.

• If greater than the specified range, replace the driver seat back heated seat element.

11. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal C and ground.

• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
• 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 CCSM.

12. Ignition ON, verify that a test lamp illuminates between the signal circuit terminal C and the low reference circuit terminal D.

• If the test lamp does not illuminate, test the low reference circuit for a short the voltage or an open/high resistance. If the circuit tests normal, replace the CCSM.

13. Ignition OFF, connect a test lamp between the cushion heater element B+ circuit terminal A and ground.
14. Ignition ON, activate the driver heated seat switch ON and OFF. The test lamp should turn ON and OFF as the switch is activated.

• 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, replace the CCSM.
• If the test lamp is always ON, test the B+ circuit for a short to voltage. If the circuit tests normal, replace the CCSM.

15. Ignition OFF, connect a test lamp between the back heater element B+ circuit terminal A and ground.
16. Ignition ON, activate the driver heated seat switch ON and OFF. The test lamp should turn ON and OFF as the switch is activated.

• 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, replace the CCSM.

17. If all circuits test normal, replace the MSM.



Front Passenger Heated Seat Malfunction
1. Ignition OFF, disconnect the X4 harness connector at the MSM.
2. Ignition ON, test for 4.50-5.50 volts between the PWM serial data circuit terminal 11 and ground.

• If less than the specified range, test the serial data circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CCSM.
• If greater than the specified range, test the serial data circuit for a short to voltage. If the circuit tests normal, replace the CCSM.

3. Ignition OFF, connect the X4 harness connector at the MSM.
4. Disconnect the harness connector at the passenger cushion heated seat element.
5. Ignition OFF, test for less than 5 ohms between the cushion heater element ground circuit terminal B and ground.

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

6. Test for less than 5 ohms between the cushion heater element terminal A and terminal B at the cushion element.

• If greater than the specified range, replace the passenger cushion heated seat element.

7. Test for 850-11.50K ohms between the cushion temperature sensor terminal C and terminal D.

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

8. Disconnect the harness connector at the passenger back heated seat element.
9. Ignition OFF, test for less than 5 ohms between the back heater element ground circuit terminal B and ground.

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

10. Test for less than 5 ohms between the seat back heater element terminal A and terminal B at the seat back element.

• If greater than the specified range, replace the passenger seat back heated seat element.

11. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal C and ground.

• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
• 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 CCSM.

12. Ignition ON, verify that a test lamp illuminates between the signal circuit terminal C and the low reference circuit terminal D.

• If the test lamp does not illuminate, test the low reference circuit for a short the voltage or an open/high resistance. If the circuit tests normal, replace the CCSM.

13. Ignition OFF, connect a test lamp between the cushion heater element B+ circuit terminal A and ground.
14. Ignition ON, activate the passenger heated seat switch ON and OFF. The test lamp should turn ON and OFF as the switch is activated.

• 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, replace the CCSM.
• If the test lamp is always ON, test the B+ circuit for a short to voltage. If the circuit tests normal, replace the CCSM.

15. Ignition OFF, connect a test lamp between the back heater element B+ circuit terminal A and ground.
16. Ignition ON, activate the passenger heated seat switch ON and OFF. The test lamp should turn ON and OFF as the switch is activated.

• 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, replace the CCSM.

17. If all circuits test normal, replace the MSM.



Repair Instructions

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

* Driver Seat and Passenger Seat Back Cushion Heater Replacement (Driver Seat and Passenger Seat Back Cushion Heater Replacement)
* Driver Seat and Passenger Seat Cushion Heater Replacement (Driver Seat and Passenger Seat Cushion Heater Replacement)
* Control Module References (Programming and Relearning) for CCSM, HVAC control module, and MSM replacement, setup, and programming


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