Pinpoint Test O: The Left Heated Seat Is Inoperative -- With Heated/Ventilated Seats

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 Wiring Diagrams CLIMATE CONTROLLED SEATS for schematic and connector information.

Normal Operation and Fault Conditions

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

DTC Fault Trigger Conditions

DTC	Description	Fault Trigger Condition
DSM B1153:4B	Driver Seat Cushion: Over Temperature	Sets when the DSM senses the left front cushion temperature has exceeded 64 deg.C (147 deg.F) for more than 4 seconds. When this DTC sets, the DSM disables the circuit until the ignition is cycled.
DSM B1156:11	Driver Seat: Circuit Short To Ground	Sets when the DSM senses the left front heater element current draw has exceeded a specified threshold. When this DTC sets, the DSM disables the circuit until the ignition is cycled.
DSM B1156:12	Driver Seat: Circuit Short To Battery	Sets when the DSM senses the left front heater circuit voltage is above a specified threshold when the driver is active. When this DTC sets, the DSM disables the circuit until the ignition is cycled.
DSM B1208:11	Driver Seat Cushion Temperature Sensor: Circuit Short To Ground	Sets when the DSM senses the left front heater sensor voltage is out-of-range low. When this DTC sets, the DSM disables the circuit until the ignition is cycled.
DSM B1208:2A	Driver Seat Cushion Temperature Sensor: Stuck in Range	Sets when the DSM senses the left front heater sensor voltage is stuck in range. When this DTC sets, the DSM disables the circuit until the ignition is cycled.

Possible Sources

Wiring, terminals or connectors
Heater mat
HVAC module
DSM

WARNING: Incorrect repair techniques or actions can cause an accidental Supplemental Restraint System (SRS) deployment. Never compromise or depart from these instructions. Failure to precisely follow all instructions could result in serious personal injury from an accidental deployment.

O1 CHECK THE HVAC (HEATING, VENTILATION AND AIR CONDITIONING) MODULE HEATED SEAT CONTROL SWITCH PID (PARAMETER IDENTIFICATION)
- Ignition ON.
- Access the HVAC and monitor the CC_SW_D_HSEATSPID
- Monitor the PID while operating the driver heated seat switch.
Did the PID change when the driver heated seat control switch was pressed and released?

Yes GO to O2

No INSTALL a new HVAC module. REFER to: Heating, Ventilation and Air Conditioning (HVAC) Control Module .

O2 CHECK FOR DSM (DRIVER FRONT SEAT MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)

Ignition OFF.

Ignition ON.

Using a diagnostic scan tool, perform DSM self-test.

Are any DSM Diagnostic Trouble Codes (DTCs) present?

Yes	For DTC B1156:11 or B1156:12, GO to O5 For DTC B1153:4B, B1208:11 or B1208:2A, GO to O7 For all other Diagnostic Trouble Codes (DTCs), REFER to the DTC Chart.

GO to O3

O3 CHECK THE HEATED SEAT VOLTAGE SUPPLY CIRCUITS FOR AN OPEN

REFER to: Supplemental Restraint System (SRS) Depowering .

Disconnect: Driver Side Airbag In-line C3051.

Disconnect: DSM Module C341D.

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C341D-1	Courtesy of FORD MOTOR COMPANY	Ground
C341D-2	Courtesy of FORD MOTOR COMPANY	Ground

Are the voltages greater than 11 volts?

Yes

GO to O4

No	REPAIR the affected circuit. GO to O16

O4 CHECK THE HEATED SEAT GROUND CIRCUITS FOR AN OPEN

Ignition OFF.

Disconnect: DSM Module C341A and C341C.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C341A-9	Courtesy of FORD MOTOR COMPANY	Ground

Positive Lead	Measurement / Action	Negative Lead
C341C-13	Courtesy of FORD MOTOR COMPANY	Ground
C341C-14	Courtesy of FORD MOTOR COMPANY	Ground

Are the resistances less than 3 ohms?

Yes

GO to O5

No	REPAIR the circuit in question. GO to O16

O5 CHECK THE HEATER ELEMENT POWER CIRCUIT FOR A SHORT TO VOLTAGE

REFER to: Supplemental Restraint System (SRS) Depowering .

Disconnect: Driver Side Airbag In-line C3051 (if not previously disconnected).

Disconnect: DSM C341B, C341C and C341D (if not previously disconnected).

Disconnect: Left Front Seat Cushion Heater C3298.

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-1	Courtesy of FORD MOTOR COMPANY	Ground

Is any voltage present?

Yes	REPAIR the circuit. GO to O16

GO to O6

O6 CHECK THE HEATER ELEMENT POWER CIRCUIT FOR AN OPEN OR SHORT TO GROUND

Ignition OFF.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-1	Courtesy of FORD MOTOR COMPANY	Ground

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-1	Courtesy of FORD MOTOR COMPANY	C341C-11

Are the resistances greater than 10, 000 ohms between the driver seat cushion heater mat and ground; and less than 3 ohms between the driver seat cushion heater mat and the DSM?

Yes

GO to O10

No	REPAIR the affected circuit. GO to O16

O7 CHECK THE HEATED SEAT TEMPERATURE SENSOR CIRCUIT FOR A SHORT TO VOLTAGE

REFER to: Supplemental Restraint System (SRS) Depowering .

Disconnect: Driver Side Airbag In-line C3051.

Disconnect: DSM C341B, C341C and C341D.

Disconnect: Left Front Seat Cushion Heater C3298.

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-2	Courtesy of FORD MOTOR COMPANY	Ground

Is any voltage present?

Yes	REPAIR the circuit. GO to O16

GO to O8

O8 CHECK THE HEATED SEAT TEMPERATURE SENSOR CIRCUIT FOR AN OPEN OR SHORT TO GROUND

Ignition OFF.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-2	Courtesy of FORD MOTOR COMPANY	Ground

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-2	Courtesy of FORD MOTOR COMPANY	C341D-15

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

Yes

GO to O9

No	REPAIR the circuit. GO to O16

O9 CHECK THE HEATED SEAT TEMPERATURE SENSOR RETURN CIRCUIT FOR AN OPEN OR SHORT TO GROUND

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-3	Courtesy of FORD MOTOR COMPANY	Ground

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-3	Courtesy of FORD MOTOR COMPANY	C341D-19

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

Yes

GO to O14

No	REPAIR the circuit. GO to O16

O10 CHECK THE HEATER ELEMENT GROUND CIRCUIT FOR AN OPEN

Disconnect: Left Front Seat Backrest Heater C3590.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3590-2	Courtesy of FORD MOTOR COMPANY	C341B-10

Are the resistances less than 3 ohms?

Yes

GO to O11

No	REPAIR the circuit. GO to O16

O11 CHECK THE CUSHION HEATED SEAT MAT FOR AN OPEN OR SHORT TO GROUND

Measure the component side resistance between:

Positive Lead	Measurement / Action	Negative Lead
Courtesy of FORD MOTOR COMPANY C3298-1, Component Side	Courtesy of FORD MOTOR COMPANY	Courtesy of FORD MOTOR COMPANY C3298-4, Component Side
Courtesy of FORD MOTOR COMPANY C3298-1, Component Side	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance between 0.6 and 2 ohms between pins 1 and 4; and greater than 10, 000 ohms between pin 1 and ground?

Yes

GO to O12

No	INSTALL a new driver seat cushion heater mat. REFER to: Seat Heater Mat Removal . GO to O16

O12 CHECK THE BACKREST HEATED SEAT MAT FOR AN OPEN OR SHORT TO GROUND

Measure the component side resistance between:

Positive Lead	Measurement / Action	Negative Lead
Courtesy of FORD MOTOR COMPANY C3590-1, Component Side	Courtesy of FORD MOTOR COMPANY	Courtesy of FORD MOTOR COMPANY C3590-2, Component Side
Courtesy of FORD MOTOR COMPANY C3590-2, Component Side	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance between 0.6 and 2 ohms between pins 1 and 2; and greater than 10, 000 ohms between pin 2 and ground?

Yes

GO to O13

No	INSTALL a new driver seat backrest heater mat. REFER to: Seat Heater Mat Removal . GO to O16

O13 CHECK THE CIRCUIT BETWEEN THE CUSHION HEATER MAT AND BACKREST HEATER MAT FOR AN OPEN AND SHORT TO GROUND

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-4	Courtesy of FORD MOTOR COMPANY	Ground

Measure:

Positive Lead	Measurement / Action	Negative Lead
C3298-4	Courtesy of FORD MOTOR COMPANY	C3590-1

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

Yes

GO to O15

No	REPAIR the circuit. GO to O16

O14 CHECK THE HEATED SEAT TEMPERATURE SENSOR FOR AN OPEN OR SHORT TO GROUND

Measure the component side resistance between:

Positive Lead	Measurement / Action	Negative Lead
Courtesy of FORD MOTOR COMPANY C3298-2, Component Side	Courtesy of FORD MOTOR COMPANY	Courtesy of FORD MOTOR COMPANY C3298-3, Component Side
Courtesy of FORD MOTOR COMPANY C3298-2, Component Side	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance between 300 and 300, 000 ohms between pins 2 and 3; and greater than 10, 000 ohms between pin 2 and ground?

Yes

GO to O15

No	INSTALL a new driver seat cushion heater mat. REFER to: Seat Heater Mat Removal . GO to O16

O15 CHECK THE DSM (DRIVER FRONT SEAT MODULE) OPERATION

Ignition OFF.

Disconnect and inspect all of the DSM connectors.

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

Reconnect the DSM connectors. Make sure they seat and latch correctly.

NOTE: Do not reconnect Driver Side Airbag In-line C3051 at this time.

Reconnect all previously disconnected connectors.

Ignition ON.

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

Is the concern still present?

Yes

CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new DSM. REFER to: Driver Front Seat Module (DSM) . GO to O16

No	The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues. GO to O16

O16 VERIFY THE SRS (SUPPLEMENTAL RESTRAINT SYSTEM) PROVES OUT SUCCESSFULLY
- REFER to: Supplemental Restraint System (SRS) Depowering .
- Connect: Driver Side Airbag In-line C3051.
- Connect all previously disconnected connectors.
- REFER to: Supplemental Restraint System (SRS) Repowering .
Did the SRS prove out successfully?

Yes Repair is complete. RETURN the vehicle to the customer.

No REFER to: Airbag Supplemental Restraint System (SRS) .