Pinpoint Test B: The Left Heated Rear Seat Is Inoperative

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

Refer to CLIMATE CONTROLLED SEATS for schematic and connector information.
Normal Operation and Fault Conditions

When the LH heated rear seat control switch is activated with the ignition ON, a ground signal is supplied to the heated seat module from the switch. When commanded ON, voltage is supplied to the heated seat switch from the heated seat module to illuminate the switch indicator. The heated seat module also supplies voltage to the LH rear seat cushion and backrest heater mats, which are connected in series. Temperature is maintained by the heated seat module using a sensor contained within the cushion heater mat. The heated seat 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 heated seat module remains ON, heating the seat and maintaining temperature until switched OFF or the ignition voltage is switched OFF.

REFER to: Rear Seats - System Operation and Component Description .

Possible Sources
- Wiring, terminals or connectors
- Heater mat
- Heated rear seat switch
- Heated rear seat module

B1 CHECK THE HEATED SEAT SWITCH INPUT

Ignition OFF.

Disconnect Heated Rear Seat Module C3304A.

While pressing and releasing the left heated rear seat switch, measure:

Positive Lead	Measurement / Action	Negative Lead
C3304A-2	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance less than 3 ohms when the switch is pressed and greater than 10, 000 ohms when released?

Yes

GO to B3

GO to B2

B2 CHECK THE HEATED SEAT SWITCH CIRCUIT FOR AN OPEN OR SHORT TO GROUND

Disconnect Heated Rear Seat Switch C3182.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3182-2	Courtesy of FORD MOTOR COMPANY	C3304A-2
C3182-2	Courtesy of FORD MOTOR COMPANY	Ground

Are the resistances less than 3 ohms between C3182-2 and C3304A-2, and greater than 10, 000 ohms between C3182-2 and ground?

Yes	INSTALL a new heated rear seat switch. REFER to: Heated Rear Seat Switch - SuperCrew .

No	REPAIR the circuit.

B3 CHECK FOR VOLTAGE TO THE HEATED SEAT MODULE

Disconnect Heated Rear Seat Module C3304B.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3304B-1	Courtesy of FORD MOTOR COMPANY	Ground

Is the voltage greater than 11 volts?

Yes

GO to B4

No	REPAIR the circuit.

B4 CHECK THE HEATER CIRCUITS AND HEATER MATS FOR AN OPEN

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3304B-4	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance between 2.5 and 4.5 ohms?

Yes

GO to B9

GO to B5

B5 CHECK THE HEATER MAT GROUND CIRCUIT FOR AN OPEN

Disconnect Left Rear Backrest Heater Mat C3168.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3168-2	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance less than 3 ohms?

Yes

GO to B6

No	REPAIR the circuit.

B6 CHECK THE HEATER CIRCUIT FOR AN OPEN OR SHORT TO GROUND

Disconnect Left Rear Cushion Heater Mat C3167.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3304B-4	Courtesy of FORD MOTOR COMPANY	C3167-1

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3304B-4	Courtesy of FORD MOTOR COMPANY	Ground

Are the resistances less than 3 ohms between C3304B-4 and C3167-1, and greater than 10, 000 ohms between C3304B-4 and ground?

Yes

GO to B7

No	REPAIR the circuit.

B7 CHECK THE CUSHION HEATER MAT FOR AN OPEN

Measure the component side resistance between:

Positive Lead	Measurement / Action	Negative Lead
Courtesy of FORD MOTOR COMPANY C3167-1, Component Side	Courtesy of FORD MOTOR COMPANY	Courtesy of FORD MOTOR COMPANY C3167-4, Component Side

Is the resistance between 1.5 and 2.5 ohms?

Yes

GO to B8

No	INSTALL a new cushion heater mat. REFER to: Seat Heater Mat Removal .

B8 CHECK FOR AN OPEN OR A SHORT TO GROUND BETWEEN THE HEATER MATS

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3167-4	Courtesy of FORD MOTOR COMPANY	C3168-1

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3167-4	Courtesy of FORD MOTOR COMPANY	Ground

Are the resistances less than 3 ohms between C3167-4 and C3168-1, and greater than 10, 000 ohms between C3167-4 and ground?

Yes	INSTALL a new backrest heater mat. REFER to: Seat Heater Mat Removal .

No	REPAIR the circuit.

B9 CHECK THE TEMPERATURE SENSOR CIRCUIT FOR A SHORT TO VOLTAGE

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3304A-3	Courtesy of FORD MOTOR COMPANY	Ground

Is any voltage present?

Yes	REPAIR the circuit.

GO to B10

B10 CHECK THE TEMPERATURE SENSOR CIRCUIT FOR A SHORT TO GROUND

Ignition OFF.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3304A-3	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance greater than 10, 000 ohms?

Yes

GO to B11

No	REPAIR the circuit.

B11 CHECK THE TEMPERATURE SENSOR AND CIRCUITS FOR AN OPEN

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3304A-3	Courtesy of FORD MOTOR COMPANY	C3304A-12

Is the resistance between 300 and 300K ohms?

Yes	INSTALL a new heated rear seat module. REFER to: Heated Rear Seat Module - SuperCrew .

GO to B12

B12 CHECK THE TEMPERATURE SENSOR FOR AN OPEN WITH THE HEATER MAT DISCONNECTED

Disconnect Left Rear Cushion Heater Mat C3167.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3304A-3	Courtesy of FORD MOTOR COMPANY	C3167-2
C3304A-12	Courtesy of FORD MOTOR COMPANY	C3167-3

Are the resistances less than 3 ohms?

Yes	INSTALL a new cushion heater mat. REFER to: Seat Heater Mat Removal .

No	REPAIR the circuit in question.