SEAT WARMER CONTROL UNIT INSPECTION

id091300976500

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 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

am6zzw00007562

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
3
Temperature of the seat warmer cannot be adjusted (See Inspection Procedure (No.3 Temperature Of Seat Warmer Cannot Be Adjusted).)
•  Seat warmer does not adjust temperature even though seat warmer LOW/HIGH switch is switched between low and high
•  Seat warmer temperature continues to rise


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 LH terminal 1D—Battery positive terminal
―  Seat warmer control unit RH terminal 1D—Battery positive terminal
•  SEAT WARMER 20 A fuse malfunction (Fuse to melt away or broken):
―  Short to ground in internal circuit of body ground
•  Seat warmer control unit LH terminal 1D—Battery positive terminal (fuse to melt away)
•  Seat warmer control unit RH terminal 1D—Battery positive terminal (fuse to melt away)
•  Poor connect the connector:
―  Seat warmer unit connector (seat cushion side) LH—Seat warmer unit connector (seat back side) LH
―  Seat warmer unit connector (seat cushion side) RH—Seat warmer unit connector (seat back side) RH
•  Open circuit in wiring harness between the following terminal:
―  Seat warmer unit (front seat cushion) LH terminal 2A—Seat warmer (front seat back) LH unit terminal A
―  Seat warmer unit (front seat cushion) RH terminal 2A—Seat warmer (front seat back) RH unit terminal A
Seat warmer control unit not operation
•  Open circuit or short to ground in wiring harness between the following terminal:
―  BCM terminal 6I—Seat warmer control unit LH terminal 1C
―  BCM terminal 6I—Seat warmer control unit RH terminal 1C
―  Seat warmer control unit LH terminal 1A—Body ground
―  Seat warmer control unit RH terminal 1A—Body ground
Seat warmer unit cannot control filament on
•  Seat warmer control LH malfunction
•  Seat warmer control RH malfunction
Seat warmer filament does not generate heat
•  Seat warmer unit (seat cushion side) LH malfunction
•  Seat warmer unit (seat back side) LH malfunction
•  Seat warmer unit (seat cushion side) RH malfunction
•  Seat warmer unit (seat back side) RH malfunction
Seat warmer control unit cannot receive operation signal
•  Seat warmer control LH malfunction
•  Seat warmer control RH malfunction
•  Open circuit or short to ground in wiring harness between the following terminal:
―  Seat warmer control unit LH terminal 1B—Seat warmer switch LH terminal H
―  Seat warmer control unit RH terminal 1B—Seat warmer switch RH terminal H
―  Seat warmer switch LH terminal J—IG2 relay (Advanced keyless and push button start system)
―  Seat warmer switch RH terminal J—IG2 relay (Advanced keyless and push button start system)
―  Seat warmer switch LH terminal J—Ignition switch (Keyless entry system)
―  Seat warmer switch RH terminal J—Ignition switch (Keyless entry system)

Diagnostic procedure

STEP

INSPECTION

ACTION
1
DETERMINE MALFUNCTIONING SYSTEM
•  Are the seat warmers on both sides not operating?
Yes
Go to the next step.
No
Go to step 8.
2
INSPECT THE SEAT WARMER POWER SUPPLY FUSE
•  Inspect the S.WARM 15 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:
―  S.WARM 15 A fuse—Seat warmer unit LH 1A
―  S.WARM 15 A fuse—Seat warmer unit RH 1A
3*
DETERMINE IF CAUSE OF MALFUNCTION IS CONTROLLER POWER SUPPLY WIRING HARNESS FOR SEAT WARMER OR OTHER CAUSE
•  Switch the ignition to off.
•  Disconnect the seat warmer control unit connector LH and RH.
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer control unit LH terminal 1D
•  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 LH and RH
4*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN SEAT WARMER CONTROL UNIT POWER SUPPLY WIRING HARNESS
•  Seat warmer control unit RH and LH connector are disconnected.
•  Switch the ignition to off.
•  Disconnect the BCM connector.
•  Verify the continuity at the following terminal:
―  Seat warmer control unit LH terminal 1D (wiring harness-side)—BCM terminal 6I
•  Is there continuity?
Yes
Inspect the BCM 3AC terminal. (See BODY CONTROL MODULE (BCM) INSPECTION.)
No
•  Repair or replace the open circuit at the following wiring harness.
―  BCM terminal 6I—Seat warmer control unit LH and RH
5*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN SEAT WARMER CONTROL UNIT POWER SUPPLY WITING HARNESS
•  Switch the ignition to off.
•  Disconnect the seat warmer control unit connector on the side that is not operating.
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal on the side that is not operating 1D
•  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 LH and RH
6*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN SEAT WARMER CONTROL UNIT CONTROL POWER SUPPLY WIRING HARNESS
•  Seat warmer control unit connector on the side that is not operating is disconnected.
•  Switch the ignition to off.
•  Disconnect the BCM connector.
•  Inspect for continuity between the following terminals (wiring harness-side):
―  Seat warmer control unit terminal on the side that is not operating 1C—BCM terminal 6I
•  Is there continuity?
Yes
Go to the next step.
No
•  Repair or replace the open circuit at the following wiring harness.
―  BCM terminal 6I—Seat warmer control unit LH and RH
7*
VERIFY IF MALFUNCTION CAUSE IS SHORT TO GROUND IN SEAT WARMER CONTROL UNIT
•  Seat warmer control unit connector on the side that is not operating is disconnected.
•  Disconnect the front climate control unit connector.
•  Inspect for continuity between the following terminals (wiring harness-side):
―  Seat warmer control unit terminal on the side that is not operating 1A—Ground
•  Is there continuity?
Yes
Go to the next step.
No
•  Inspect the open circuit following.
―  Seat warmer unit 1B terminal—GND
•  Inspect the GND connector terminals for poor connection.
•  Repair or replace the malfunction.
8
VERIFY IF MALFUNCTION CAUSE IS SEAT WARMER SWITCH OR SEAT WARMER UNIT
•  Seat warmer control unit connector on the side that is not operating is disconnected.
•  Engine start.
•  Operate the seat warmer switch on the side that is not operating while measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal 1B
•  Is the voltage normal?
―  Standard voltage:
•  Seat warmer switch Lo: Approx. 4.7 V
•  Seat warmer switch Hi: Approx. 1.7 V
Yes
Go to step 13.
No
Go to the next step.
9*
VERIFY IF MALFUNCTION CAUSE IS SEAT WARMER SWITCH
•  Inspect the seat warmer switch. (See SEAT WARMER SWITCH INSPECTION.)
•  Is the seat warmer switch normal?
Yes
Go to the next step.
No
Replace the seat warmer switch. (See SEAT WARMER SWITCH REMOVAL/INSTALLATION.)
10*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN WIRING HARNESS OF SEAT WARMER SWITCH SIGNAL
•  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 1B—Seat warmer switch terminal H
•  Is the voltage B+?
Yes
Go to the next step.
No
Repair or replace the open circuit in wiring harness.
11*
VERIFY IF MALFUNCTION CAUSE IS SHORT TO GROUND IN SEAT WARMER SWITCH
•  Is the operation of the air conditioner (mode, switch the temperature) normal
Yes
Go to the next step.
No
•  Inspect the malfunction following.
―  A/C 10 A FUSE
•  Repair or replace the short to ground in wiring harness.
―  A/C 10 A FUSE—Climate control unit LH terminal J
―  A/C 10 A FUSE—Seat warmer switch LH terminal J
―  A/C 10 A FUSE—Seat warmer switch RH terminal J
12*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN SEAT WARMER SWITCH
•  Switch the ignition to off.
•  Disconnect the seat warmer switch connector on the side that is not operating.
•  Remove the A/C 20 A fuse.
•  Inspect for continuity between the following terminals (wiring harness-side):
―  A/C 20 A fuse—Seat warmer switch terminal J
•  Is there continuity?
Yes
Replace the seat warmer switch on the side that is not operating. (See SEAT WARMER SWITCH REMOVAL/INSTALLATION.)
No
Repair or replace the open circuit in wiring harness.
13*
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.
14*
VERIFY IF MALFUNCTION CAUSE IS SEAT WARMER SWITCH
•  Inspect the seat warmer unit (seat cushion side and seat back side). (See SEAT WARMER UNIT INSPECTION.)
•  Is the seat warmer unit (seat cushion side and seat back side) normal?
Yes
Go to the next step.
No
Replace the seat warmer unit (seat cushion side or seat back side). (See FRONT SEAT CUSHION TRIM REMOVAL/INSTALLATION.) (See FRONT SEAT BACK TRIM REMOVAL/INSTALLATION.)
15*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN WIRING HARNESS OF SEAT WARMER UNIT CONTROL CIRCUIT
•  Seat warmer control unit connector on the side that is not operating is disconnected.
•  Switch the ignition to off.
•  Disconnect the seat warmer unit (seat back side) connector on the side that is operating.
•  Verify the continuity at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal on the side that is not operating 2D—front climate control unit connector 1U
―  Passenger-side seat warmer does not operate:
•  Seat warmer unit terminal on the side that is not operating 1C—Seat warmer unit (seat back side) connector B
•  Is there continuity?
Yes
Replace the seat warmer unit on the side that is not operating. (Seat warmer control unit can not to
ON for the seat warmer unit.)
No
Repair or replace the open circuit in wiring harness.


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
Seat warmer switch is always ON
•  Seat warmer switch malfunction
Seat warmer control unit falsely detects seat warmer switch is ON
•  Seat warmer control unit LH malfunction
•  Seat warmer control unit RH malfunction
•  Short circuit in wiring harness between the following terminal:
―  Seat warmer control unit LH terminal 1B—Seat warmer switch terminal H
―  Seat warmer control unit RH terminal 1B—Seat warmer switch terminal H
Seat warmer unit is in constant ON control status
•  Seat warmer control unit LH malfunction
•  Seat warmer control unit RH malfunction
•  Short to ground or short circuit in wiring harness between the following terminal:
―  Seat warmer control unit LH terminal 2D—Seat warmer unit (seat back side) terminal B
―  Seat warmer control unit RH terminal 2D—Seat warmer switch terminal H

Diagnostic procedure

STEP

INSPECTION

ACTION
1*
DETERMINE IF MALFUNCTION CAUSE IS SIGNAL OF SEAT WARMER SWITCH OR MALFUNCTION IN CONTROL SIGNAL OF SEAT WARMER UNIT
•  Switch the ignition to off.
•  Disconnect the seat warmer control unit connector on the side that is malfunction.
•  Engine start.
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer control unit on the side that is malfunction terminal 1B
―  Is the voltage normal?
Yes
Go to the next step.
No
Go to step 4.
2
VERIFY IF MALFUNCTION CAUSE IS SEAT WARMER SWITCH
•  Inspect the seat warmer switch. (See SEAT WARMER SWITCH INSPECTION.)
•  Is the seat warmer switch normal?
Yes
Go to the next step.
No
Replace the seat warmer switch. (See SEAT WARMER SWITCH REMOVAL/INSTALLATION.)
3*
VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN WIRING HARNESS OF SEAT WARMER SWITCH SIGNAL
•  Disconnect the seat warmer switch and seat warmer control unit connector on the side that is malfunction.
•  Engine start.
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer switch terminal on the side that is malfunction H—GND
•  Is the voltage 1.0 or more?
Yes
Repair or replace for a short to ground in the wiring harness.
No
Replace the seat warmer control unit on the side that is malfunction.
4*
VERIFY IF MALFUNCTION CAUSE IS SHORT CIRCUIT FROM CONTROL SIGNAL WIRING HARNESS OF SEAT WARMER TO OTHER WIRING HARNESS
•  Seat warmer control unit connector on the side that is malfunction is disconnected.
•  Engine start.
•  Disconnect the seat warmer unit (front seat back) connector on the side that is not operating.
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal on the side that is malfunction 2D—GND
•  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.
5*
VERIFY IF MALFUNCTION CAUSE IS SHORT CIRCUIT FROM CONTROL SIGNAL WIRING HARNESS OF SEAT WARMER TO GND WIRING HARNESS
•  Seat warmer control unit connector on the side that is malfunction is disconnected.
•  Verify the continuity at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal on the side that is malfunction 2D—GND
•  Is there continuity?
Yes
Repair for a short to ground in the wiring harness.
No
Replace the seat warmer control unit on the side that is malfunction.


Inspection Procedure (No.3 Temperature Of Seat Warmer Cannot Be Adjusted)

No.3

Temperature of seat warmer cannot be adjusted
DETECTION
•  Seat warmer does not adjust temperature even though seat warmer Lo/Hi switch is switched between low and high
•  Seat warmer temperature continues to rise
POSSIBLE CAUSE
Seat warmer switch does not Lo/Hi switched
•  Seat warmer switch LH malfunction
•  Seat warmer switch RH malfunction
Seat warmer control unit falsely detects always seat warmer switch to Lo or Hi
•  Seat warmer control unit LH malfunction
•  Seat warmer control unit RH malfunction
•  Short to ground in wiring harness between the following terminal:
―  Seat warmer control unit LH terminal 1B—Seat warmer switch terminal H to other wiring harness
―  Seat warmer control unit RH terminal 1B—Seat warmer switch terminal H to other wiring harness
Seat warmer control unit cannot control seat warmer unit
•  Seat warmer control unit LH malfunction
•  Seat warmer control unit RH malfunction
•  Thermostat (Built-in seat warmer unit LH) malfunction
•  Thermostat (Built-in seat warmer unit RH) malfunction
•  Short to ground or short circuit in wiring harness between the following terminal:
―  Seat warmer control unit LH terminal 2D—Seat warmer unit (seat back side)
―  Seat warmer control unit RH terminal 2D—Seat warmer unit (seat back side)

Diagnostic procedure

STEP

INSPECTION

ACTION
1*
VERIFY IF MALFUNCTION CAUSE IS SIGNAL OF SEAT WARMER SWITCH OR THE OTHER
•  Switch the ignition to off.
•  Disconnect the seat warmer control unit connector on the side that is malfunction.
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal on the side that is not operating 1B
•  Is the seat warmer switch normal?
―  Standard voltage:
•  Seat warmer switch OFF: B+
•  Seat warmer switch Lo: Approx. 4.7 V
•  Seat warmer switch Hi: Approx. 1.7 V
Yes
Go to step 3.
No
Go to the next step.
2
VERIFY IF MALFUNCTION CAUSE IS SEAT WARMER SWITCH
•  Inspect the seat warmer switch. (See SEAT WARMER SWITCH INSPECTION.)
•  Is the seat warmer switch normal?
Yes
Go to the next step.
No
Replace the seat warmer switch. (See SEAT WARMER SWITCH REMOVAL/INSTALLATION.)
3*
VERIFY IF MALFUNCTION CAUSE IS SHRT CIRCUIT IN WIRING HARNESS OF SEAT WARMER SWITCH SIGNAL
•  Seat warmer switch and seat warmer control unit connector on the side that is malfunction disconnected.
•  Engine start.
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer switch terminal on the side that is malfunction H—Body ground
•  Is the voltage 1.0 or more?
Yes
Repair or replace for a short to ground in the wiring harness.
No
Replace the seat warmer control unit.
4
VERIFY IF MALFUNCTION CAUSE IS THERMOSTAT (BILT-IN SEAT WARMER UNIT)
•  Inspect the seat warmer unit (seat cushion side). (See SEAT WARMER UNIT INSPECTION.)
•  Is the seat warmer unit (seat cushion side) normal?
Yes
Go to the next step.
No
Replace the seat warmer unit (seat cushion side). (See FRONT SEAT CUSHION TRIM REMOVAL/INSTALLATION.)
5*
VERIFY IF MALFUNCTION CAUSE IS SHRT CIRCUIT IN WIRING HARNESS OF SEAT WARMER UNIT CONTROL SIGNAL
•  Seat warmer control unit connector on the side that is malfunction disconnected.
•  Engine start.
•  Measure the voltage at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal on the side that is malfunction 2D—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.
6*
VERIFY IF MALFUNCTION CAUSE IS SHORT CIRCUIT FROM CONTROL SIGNAL WIRING HARNESS OF SEAT WARMER TO GND WIRING HARNESS
•  Seat warmer control unit connector on the side that is malfunction disconnected.
•  Verify the continuity at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal on the side that is malfunction 2D—Body ground
•  Is there continuity?
Yes
Repair or replace for a short to ground in the wiring harness.
No
Go to the next step.
7*
VERIFY IF MALFUNCTION CAUSE IS CONTROL SIGNAL WIRING HARNESS OF THERMOSTAT (BILT-IN SEAT WARMER UNIT)
•  Seat warmer control unit connector on the side that is malfunction disconnected.
•  Verify the continuity at the following terminal (wiring harness-side):
―  Seat warmer control unit terminal on the side that is malfunction 2A—Body ground
•  Is there continuity?
Yes
Repair or replace for a short to ground in the wiring harness.
No
Replace the seat warmer control unit.