SEAT WARMER CONTROL UNIT INSPECTION

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Warning
•  Handling a front seat (with built-in side air bag) improperly can accidentally operate (deploy) the air bag, which may seriously injure you. Read the service warnings/cautions before handling a front seat (with built-in side air bag). (See AIR BAG SYSTEM SERVICE WARNINGS.) (See AIR BAG SYSTEM SERVICE CAUTIONS.)
Caution
•  After removing a front seat, do not operate the slider lever. If the slider lever is operated, the left and right slide positions will deviate, and the slide adjuster may be damaged after the front seat is installed.
•  Verify that there are no malfunctions in the sliding mechanism after installing a front seat.
•  When performing the procedure with a front seat removed from the vehicle, perform the procedure on a clean rag so as not to damage or soil the seat.

Forward

•  When performing an asterisked (*) troubleshooting inspection, shake the wiring harness and connectors while performing the inspection to discover whether poor contact points are the cause of any intermittent malfunction. If there is a problem, inspect to make sure connectors, terminals and wiring harnesses are connected correctly and undamaged.

System Diagram

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Symptom Trouble Shooting Index

No.

Troubleshooting item

Description
1
Seat warmer function is inoperative (See Inspection Procedure (No.1 Seat Warmer Function Is Inoperative).)
Seat warmer does not warm seat even though seat warmer switch is on
2
Seat warmer always operations (See Inspection Procedure (No.2 Seat Warmer Always Operations).)
Seat warmer warms seat even though seat warmer switch is off


Inspection Procedure (No.1 Seat Warmer Function Is Inoperative)

No.1

Seat warmer function is inoperative
DETECTION
Seat warmer does not warm seat even though seat warmer switch is on
POSSIBLE CAUSE
The power supply is not supplied to filament of seat warmer
•  Open circuit in seat warmer control unit power supply circuit:
―  Seat warmer control unit terminal O—Battery positive terminal
―  Seat warmer control unit terminal M—Battery positive terminal
•  SEAT WARM 20 A fuse malfunction (Fuse to melt away or broken):
―  Seat warmer control unit terminal O—Battery positive terminal (fuse to melt away)
―  Seat warmer control unit terminal M—Battery positive terminal (fuse to melt away)
•  Poor connect the connector:
―  Driver-side seat warmer unit connector—Seat warmer control unit connector
―  Passenger-side seat warmer unit connector—Seat warmer control unit connector
•  Open circuit in wiring harness between the following terminal:
―  Driver-side seat warmer unit terminal P—Driver-side seat warmer unit terminal A
―  Passenger-side seat warmer unit terminal N—Passenger-side seat warmer unit terminal B
Seat warmer control unit not operation
•  Open circuit or short to ground in wiring harness between the following terminal:
―  Front body control module (FBCM) terminal 1C—Seat warmer control unit terminal K
―  Seat warmer control unit terminal H—Body ground
―  Seat warmer control unit terminal G—Body ground
Seat warmer unit cannot control filament on
•  Seat warmer control malfunction
Seat warmer filament does not generate heat
•  Driver-side seat warmer unit (seat cushion side) malfunction
•  Driver-side seat warmer unit (seat back side) malfunction
•  Passenger-side seat warmer unit (seat cushion side) malfunction
•  Passenger-side seat warmer unit (seat back side) malfunction
Seat warmer control unit cannot receive operation signal
•  Seat warmer control unit malfunction
•  Open circuit or short to ground in wiring harness between the following terminal:
―  Seat warmer control unit terminal I—Climate control unit terminal 1E (with full-auto air conditioner)
―  Seat warmer control unit terminal I—Indicator unit terminal D (with manual air conditioner)

Diagnostic procedure

STEP

INSPECTION

ACTION
1
PERFORM DTC INSPECTION
•  Perform instrument cluster and climate control unit DTC inspection.
•  Verify the instrument cluster DTC inspection.
•  Are DTCs and error codes output?
Yes
Perform the diagnosis according to the inspection procedure for each code.
No
Go to the next step.
2
DETERMINE IF THE MALFUNCTION CAUSE IS THE SEAT WARMER SWITCH
•  Select either Low, Mid, or High on the seat warmer switch.
•  Does the seat warmer switch LED illuminate?
Yes
Go to the next step.
No
Inspect the climate control unit or indicator unit.
(See CLIMATE CONTROL UNIT INSPECTION [FULL-AUTO AIR CONDITIONER].)
(See INDICATOR UNIT INSPECTION.)
3
DETERMINE MALFUNCTIONING SYSTEM
•  Does either the left or right seat warmer operate?
Yes
Go to step 9.
No
Go to the next step.
4
INSPECT THE SEAT WARMER CONTROL UNIT POWER SUPPLY FUSE
•  Inspect the SEAT WARM 20 A fuse.
•  Is the fuse normal?
Yes
Go to the next step.
No
•  If the fuse is deterioration:
―  Replace the malfunctioning fuse.
•  If the fuse is melt
Repair the short to ground in wiring harness between the following terminals:
―  SEAT WARM 20 A fuse—Seat warmer control unit O
―  SEAT WARM 20 A fuse—Seat warmer control unit M
5*
DETERMINE IF CAUSE OF MALFUNCTION IS CONTROLLER POWER SUPPLY WIRING HARNESS FOR SEAT WARMER OR OTHER CAUSE
•  Switch the ignition off (LOCK).
•  Disconnect the seat warmer control unit connector.
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal M
―  Seat warmer control unit terminal O
•  Is the voltage B+?
Yes
Go to the next step.
No
•  Repair or replace the open circuit at the following wiring harness.
―  SEAT WARMER 20 A fuse—Seat warmer control unit
6*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN SEAT WARMER CONTROL UNIT POWER SUPPLY WIRING HARNESS
•  Seat warmer control unit connector are disconnected.
•  Switch the ignition ON (engine off or on).
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal K
•  Is the voltage B+?
Yes
Go to the next step.
No
•  Inspect the front body control module (FBCM) 1C terminal. (See FRONT BODY CONTROL MODULE (FBCM) INSPECTION.)
•  Repair or replace the open circuit at the following wiring harness.
―  Front body control module (FBCM) terminal 1C—Seat warmer control unit terminal K
7*
INSPECT FOR OPEN CIRCUIT IN SEAT WARMER CONTROL UNIT GROUND CIRCUIT
•  Seat warmer control unit connector on the side that is not operating is disconnected.
•  Inspect for continuity between the following terminals (wiring harness-side):
―  Seat warmer control unit terminal on the side that is not operating H—Ground
―  Seat warmer control unit terminal on the side that is not operating G—Ground
•  Is there continuity?
Yes
Go to the next step.
No
•  Inspect the open circuit following.
―  Seat warmer unit terminal H—GND
―  Seat warmer unit terminal G—GND
•  Inspect the GND connector terminals for poor connection.
•  Repair or replace the malfunction.
8*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN WIRING HARNESS OF SEAT WARMER SWITCH SIGNAL
•  Seat warmer control unit connector is disconnected.
•  Inspect for continuity between the following terminals (wiring harness-side):
With full-auto air conditioner
―  Seat warmer control unit terminal I—Climate control terminal 1E
With manual air conditioner
―  Seat warmer control unit terminal I—Indicator unit terminal D
•  Is there continuity?
Yes
Go to the next step.
No
•  Inspect the open circuit following.
―  Seat warmer control unit terminal I—Climate control terminal 1E
―  Seat warmer control unit terminal I—Indicator unit terminal D
9*
INSPECT SEAT WARMER CONTROL UNIT AND SEAT WARMER UNIT CONNECTOR
•  Disconnect the seat warmer control unit and seat warmer unit connector on the side not operating.
•  Inspect the seat warmer control unit and seat warmer unit connector terminals for poor connection (such as damaged/pulled-out pins, and corrosion).
•  Is there any malfunction?
Yes
Repair or replace the malfunctions.
No
Go to the next step.
10*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN WIRING HARNESS OF SEAT WARMER UNIT CIRCUIT
•  Switch the ignition off (LOCK).
•  Disconnect the seat warmer control unit connector.
•  Inspect for continuity between the following terminals (wiring harness-side):
―  Driver-side seat warmer unit terminal P—A
―  Passenger-side seat warmer unit terminal N—B
•  Is there continuity?
Yes
Go to the next step.
No
Replace the seat warmer unit.
11
DETERMINE IF THE MALFUNCTION CAUSE IS SEAT WARMER CONTROL UNIT
With full-auto air conditioner
―  Replace the climate control unit.
With manual air conditioner
―  Replace the indicator unit.
•  Does the seat warmer system operate?
Yes
Troubleshooting completed.
No
Replace the seat warmer control unit.


Inspection Procedure (No.2 Seat Warmer Always Operations)

No.2

Seat warmer always operations
DETECTION
Seat warmer warms seat even though seat warmer switch is off
POSSIBLE CAUSE
•  Short circuit in wiring harness between the following terminal.
―  seat warmer control unit terminal N and passenger-side seat warmer unit terminal G.
―  seat warmer control unit terminal P and driver-side front seat warmer unit terminal 6B.
•  Passenger-side seat warmer unit malfunction.
•  Driver-side seat warmer unit malfunction.
•  Indicator unit malfunction.
•  Seat warmer control unit malfunction.

Diagnostic procedure

STEP

INSPECTION

ACTION
1*
INSPECT SEAT WARMER UNIT CIRCUIT FOR SHORT TO POWER SUPPLY
•  Disconnect the seat warmer control unit connector.
•  Measure the voltage between passenger-side front seat warmer unit terminal G and body ground.
•  Measure the voltage between driver-side front seat warmer unit terminal 6B and body ground.
•  Is the voltage 1.0 or more?
Yes
Repair or replace for a short to ground in the wiring harness.
No
Go to the next step.
2
INSPECT SEAT WARMER UNIT
•  Inspect the seat warmer unit.
(See SEAT WARMER UNIT INSPECTION.)
•  Is the front seat warmer unit normal?
Yes
Go to the next step.
No
Replace the front seat back pad.
(See FRONT SEAT CUSHION TRIM REMOVAL/INSTALLATION.)
3
INSPECT INDICATOR UNIT
•  Inspect the indicator unit.
(See INDICATOR UNIT INSPECTION.)
•  Is the indicator unit nomal?
Yes
Replace the seat warmer control unit.
(See SEAT WARMER CONTROL UNIT REMOVAL/INSTALLATION.)
No
Replace the indicator unit.
(See INDICATOR UNIT REMOVAL/INSTALLATION.)