Diagnostic Routine M

Diagnostic Routine M

Diagnostic Overview

The Heated Seat is Inoperative or Does Not Operate Correctly - Passenger

Refer to Wiring Diagram Set 119 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

The engine must be running for the heated seat system to operate. The driver and passenger heated seat buttons are selected from the touchscreen interface, which initiates the CAN (Controller Area Network) communication to request heated seat operation. REFER to Network Message Chart . Upon receiving the request, the HVAC (Heating, Ventilation, and Air Conditioning) module supplies voltage to the appropriate driver and/or passenger seat cushion and backrest heater mats, which are connected in series. Temperature is maintained by the HVAC (Heating, Ventilation, and Air Conditioning) module using a sensor contained within the cushion heater mat. The HVAC (Heating, Ventilation, and Air Conditioning) module supplies a reference voltage to the temperature sensor and monitors the return signal from the temperature sensor for controlling current flow to the heater mats. The HVAC (Heating, Ventilation, and Air Conditioning) module remains on, heating the seat and maintaining temperature until commanded off from the FCIM (Front Controls Interface Module) or touchscreen interface (or until the ignition is turned OFF).

DTC Fault Trigger Conditions

Visual Inspection and Diagnostic Pre-checks

Make sure BJB (Battery Junction Box) fuse 28 (30A) is OK.

Pinpoint Test

1. CHECK FOR HVAC (Heating, Ventilation, and Air Conditioning) MODULE DTCs (Diagnostic Trouble Codes)

1. Ignition ON.

2. Using a scan tool, perform HVAC (Heating, Ventilation, and Air Conditioning) module self-test.

Were any DTCs (Diagnostic Trouble Codes) retrieved during the self-test?

2. CHECK THE TOUCHSCREEN CONTROLS OPERATION

1. Start the engine.

2. Select each audio and climate control function using the touchscreen controls.

Do all touchscreen controls operate?

3. CHECK THE HEATER ELEMENT POWER CIRCUIT FOR AN OPEN OR SHORT TO GROUND

1. WARNING: Turn the ignition OFF and wait one minute to deplete the backup power supply. Failure to follow this instruction may result in serious personal injury or death in the event of an accidental deployment.

Ignition OFF.

2. Disconnect: Passenger Seat Side Air Bag C339.

3. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228B.

4. Disconnect: Passenger Cushion Heater Mat C334.

5. Measure:

Is the resistance greater than 10,000 ohms between the passenger seat cushion heater mat and ground; and less than 3 ohms between the passenger seat cushion heater mat and the HVAC (Heating, Ventilation, and Air Conditioning) module?

4. CHECK THE HEATED SEAT TEMPERATURE SENSOR CIRCUIT FOR AN OPEN OR SHORT TO GROUND

1. WARNING: Turn the ignition OFF and wait one minute to deplete the backup power supply. Failure to follow this instruction may result in serious personal injury or death in the event of an accidental deployment.

Ignition OFF.

2. Disconnect: Passenger Seat Side Air Bag C339.

3. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228B.

4. Disconnect: Passenger Cushion Heater Mat C334.

5. Measure:

5. CHECK THE HEATED SEAT TEMPERATURE SENSOR RETURN CIRCUIT FOR AN OPEN OR SHORT TO GROUND

1. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228A.

2. Measure:

6. CHECK THE HEATED SEAT CIRCUITS FOR A SHORT TO VOLTAGE

1. WARNING: Turn the ignition OFF and wait one minute to deplete the backup power supply. Failure to follow this instruction may result in serious personal injury or death in the event of an accidental deployment.

Ignition OFF.

2. Disconnect: Passenger Seat Side Air Bag C339.

3. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228A and C228B.

4. Disconnect: Passenger Cushion Heater Mat C334.

5. Ignition ON.

6. Measure:

Is any voltage present on any circuits?

7. CHECK THE HEATER ELEMENT GROUND CIRCUIT FOR AN OPEN

1. Disconnect: Passenger Seat Backrest Heater Mat C335.

2. Measure:

Is the resistance less than 3 ohms?

8. CHECK CUSHION HEATED SEAT MAT FOR AN OPEN AND A SHORT TO GROUND

1. Measure:

Is the resistance greater than 10,000 ohms between the passenger seat cushion heater mat and ground; and between 1.2 and 2.2 ohms between the passenger seat cushion heater mat pins?

9. CHECK THE BACKREST HEATED SEAT MAT FOR AN OPEN OR SHORT TO GROUND

1. Measure:

Is the resistance greater than 10,000 ohms between the passenger seat backrest heater mat and ground; and between 1.2 and 2.2 ohms between the passenger seat backrest heater mat pins?

10. CHECK FOR A SHORT TO GROUND OR OPEN CIRCUIT BETWEEN THE BACKREST AND CUSHION HEATER MAT

1. Measure:

Is the resistance greater than 10,000 ohms between the passenger seat cushion heater mat and ground; and less than 3 ohms between the passenger seat cushion heater mat and the backrest heater mat?

11. CHECK THE HEATED SEAT TEMPERATURE SENSOR FOR AN OPEN OR SHORT TO GROUND

1. Measure:

Is the resistance between 725 ohms and 170,000 ohms between passenger seat cushion heater mat pins; and greater than 10,000 ohms between passenger seat cushion heater mat and ground?

12. CHECK FOR CORRECT HVAC (Heating, Ventilation, and Air Conditioning) MODULE OPERATION

1. Ignition OFF.

2. Disconnect and inspect all HVAC (Heating, Ventilation, and Air Conditioning) module connectors.

3. Repair:

- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins as necessary
- pushed-out pins - install new pins as necessary

4. Reconnect the HVAC (Heating, Ventilation, and Air Conditioning) module connectors. Make sure they seat and latch correctly.

5. Connect: Passenger Seat Cushion Heater Mat C334 (if previously disconnected).

6. Connect: Passenger Seat Backrest Heater Mat C335 (if previously disconnected).

7. Operate the system and determine if the concern is still present.

Is the concern still present?

13. CHECK FOR SRS (Supplemental Restraint System) DTCs (Diagnostic Trouble Codes)

1. WARNING: Turn the ignition OFF and wait one minute to deplete the backup power supply. Failure to follow this instruction may result in serious personal injury or death in the event of an accidental deployment.

Ignition OFF.

2. Connect: Passenger Seat Side Air Bag C339.

3. Connect: Passenger Seat Cushion Heater Mat C334 (if previously disconnected).

4. Connect: Passenger Seat Backrest Heater Mat C335 (if previously disconnected).

5. Ignition ON.

6. Using a scan tool, clear the RCM (Restraints Control Module) DTCs (Diagnostic Trouble Codes).

7. Cycle the ignition OFF then ON.

8. Using a scan tool, perform RCM (Restraints Control Module) self-test.

Are any RCM (Restraints Control Module) DTCs (Diagnostic Trouble Codes) retrieved during self-test?