Pinpoint Test Q: The Heated Seats are Inoperative - Driver and Front Passenger
Seats
Pinpoint Test Q: The Heated Seats are Inoperative - Driver and Front Passenger
Refer to Wiring Diagram Set 119 (Fusion/Milan/MKZ, Fusion Hybrid, Milan Hybrid, MKZ Hybrid), Climate Controlled Seats for schematic and connector information. Diagrams By Number
Normal Operation
The engine must be running for the heated seat system to operate. When the driver or passenger heated seat button is pressed, a momentary ground signal is sent on the driver or passenger request circuit to turn the heated seat system on or off. The heated seat module monitors temperature sensors contained within the cushion heater mats. The temperature sensors share the same return circuit to the heated seat module. If the temperature sensor return circuit opens (resistance greater than 300,000 ohms), the heated seat module will disable the outputs to both seats.
The Front Controls Interface Module (FCIM) (with navigation), HVAC module and heated seat module must be communicating correctly for the system to operate correctly. PIDs are available to check heated seat switch operation in the FCIM (with navigation) and HVAC module (with and without navigation).
Normal heat cycle may require several minutes to initially warm the seat. The seat should be occupied to correctly test for normal operation. Temperature measuring devices do not provide an accurate method for testing heated seat operation as surface temperatures are subject to human and environmental characteristics. Correct testing requires heater mat resistance measurements which have tight tolerances affecting the length of time for the heater mats to reach maximum operating temperature.
The heated seat module does not report DTCs. If a fault is detected, the module will disable the affected seat(s) and indicator(s). After the fault is corrected, the heated seat module needs to be reset by cycling the ignition.
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- Medium Speed Controller Area Network (MS-CAN) fault
- FCIM (if equipped)
- Heated seat module
- HVAC module
PINPOINT TEST Q: THE HEATED SEATS ARE INOPERATIVE - DRIVER AND FRONT PASSENGER
NOTE: If a seat equipped with a seat mounted side air bag is being serviced, the Supplemental Restraint System (SRS) must be depowered. Refer to Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering.
NOTE: The air bag warning lamp illuminates when the Restraints Control Module (RCM) fuse is removed and the ignition switch is ON. This is normal operation and does not indicate an SRS fault.
NOTE: The SRS must be fully operational and free of faults before releasing the vehicle to the customer.
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Q1 CHECK HEATED SEAT OPERATION
- Ignition OFF.
- Start the engine.
- Verify both heated seats do not heat.
- Does either heated seat operate?
Yes
GO to Symptom Chart to diagnose the heated seat is inoperative/does not operate correctly - driver or the heated seat is inoperative/does not operate correctly - passenger. Symptom Related Diagnostic Procedures
No
GO to Q2.
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Q2 CHECK HEATED SEAT INDICATOR ILLUMINATION
- Ignition OFF.
- Start the engine.
- Verify system indicator illumination.
- When pressing and releasing each heated seat button individually, does any heated seat indicator illuminate or flash and then turn off?
Yes
GO to Q7.
No
For vehicles with navigation, GO to Q3.
For vehicles without navigation, GO to Q4.
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Q3 RETRIEVE THE FCIM DTCs
- Enter the following diagnostic mode on the scan tool: Self Test - FCIM.
- Are any FCIM DTCs retrieved?
Yes
For all FCIM DTCs, REFER to the Master DTC Chart in Information and Entertainment Systems Testing and Inspection.
No
GO to Q4.
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Q4 RETRIEVE THE HVAC MODULE DTCs
- Enter the following diagnostic mode on the scan tool: Self Test - HVAC Module.
- Are any HVAC module DTCs retrieved?
Yes
For any HVAC module DTCs, REFER to the HVAC Module DTC Chart. HVAC Module DTC Chart
No
For vehicles with navigation, GO to Q5.
For vehicles without navigation, GO to Q6.
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Q5 MONITOR THE FCIM PIDs AND CHECK INPUTS
- Enter the following diagnostic mode on the scan tool: DataLogger - FCIM - PIDs.
- Driver Heated Seat (CC_SW_D_HSEATS)
- Passenger Heated Seat (CC_SW_P_HSEATS)
- Monitor the FCIM PIDs while individually pushing the driver and passenger heated seat buttons.
- Do the PID values agree with the switch button positions?
Yes
GO to Q6.
No
INSTALL a new FCIM. REFER to Information and Entertainment Systems Service and Repair. TEST the system for normal operation.
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Q6 MONITOR THE HVAC MODULE PIDs AND CHECK INPUTS
- Enter the following diagnostic mode on the scan tool: DataLogger - HVAC Module - PIDs.
- Driver Heated Seat (CC_SW_D_HSEATS)
- Passenger Heated Seat (CC_SW_P_HSEATS)
- Monitor HVAC module PIDs while individually pushing the driver and passenger heated seat buttons.
- Do the PID values agree with the switch button positions?
Yes
The fault is intermittent, CHECK for causes of the intermittent fault. INSPECT the connectors, terminals and wiring. ATTEMPT to recreate the fault by flexing the wire harness and operating the system. CHECK the electrical connectors for corrosion, poor pin contact or pushed-out pins. REPAIR any intermittent concerns found and TIGHTEN any loose connector pins. REPEAT the self-test. CLEAR the DTCs. CHECK the system for normal operation.
No
INSTALL a new HVAC module. TEST the system for normal operation.
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Q7 CHECK VOLTAGE TO THE HEATED SEAT MODULE
- Ignition OFF.
- Depower the SRS. Refer to Supplemental Restraint System (SRS) Depowering and Repowering in the General Procedures portion of Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering.
- Disconnect: Passenger Seat Side Air Bag Module C313.
- Disconnect: Heated Seat Module C3304B.
- WARNING: Make sure no one is in the vehicle and there is nothing blocking or placed in front of any air bag module when the battery is connected. Failure to follow these instructions may result in serious personal injury in the event of an accidental deployment.
- Connect the battery ground cable. Refer to Battery, Mounting and Cables Battery Disconnect.
- Ignition ON.
- Measure the voltage between:
- heated seat module C3304B-1, circuit SBP18 (YE/RD), harness side and ground.
- heated seat module C3304B-2, circuit CBP35 (YE/GY), harness side and ground.
- Are the voltages greater than 10 volts?
Yes
GO to Q8.
No
VERIFY Smart Junction Box (SJB) fuses 18 (20A) and 35 (10A) are OK. If OK, REPAIR the affected circuit. If not OK, Refer to the Wiring Diagrams to identify the possible causes of the circuit short. TEST the system for normal operation. Diagrams By Number
DISCONNECT the battery ground cable.
CONNECT passenger seat side air bag module C313.
REPOWER the SRS. REFER to Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering.
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Q8 CHECK THE HEATED SEAT MODULE GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between heated seat module C3304B-5, circuit GD139 (BK/YE), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to Q9.
No
REPAIR the circuit. TEST the system for normal operation.
DISCONNECT the battery ground cable.
CONNECT passenger seat side air bag module C313.
REPOWER the SRS. REFER to Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering.
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Q9 CHECK HEATED SEAT MODULE SENSOR RETURN CIRCUIT FOR AN OPEN
- Disconnect: Heated Seat Module C3304A.
- Disconnect: Passenger Seat Cushion Heater C334.
- Measure the resistance between heated seat module C3304A-12, circuit RHS05 (YE/VT), harness side and passenger seat cushion heater C334-4, circuit RHS05 (YE/VT), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new heated seat module. REFER to Heated Seat Module Heated Seat Module. TEST the system for normal operation.
DISCONNECT the battery ground cable.
CONNECT passenger seat side air bag module C313.
REPOWER the SRS. REFER to Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering.
No
REPAIR the circuit. TEST the system for normal operation.
DISCONNECT the battery ground cable.
CONNECT passenger seat side air bag module C313.
REPOWER the SRS. REFER to Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering.
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