SEAT WARMER 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 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.

Seat Cushion

Wiring diagram

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Symptom trouble shooting index

No. | Troubleshooting item | Description
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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 LO/HI 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
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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 or short to ground in seat warmer unit power supply circuit: ― Seat warmer unit LH terminal 1A—Battery positive terminal ― Seat warmer unit RH terminal 1A—Battery positive terminal • S.WARM 15 A fuse malfunction • 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 not operation • Open circuit in wiring harness between the following terminal: ― BCM terminal 6N—Seat warmer unit LH terminal 1E ― BCM terminal 6N—Seat warmer unit RH terminal 1E ― Seat warmer unit LH terminal 1B—body ground ― Seat warmer unit RH terminal 1B—body ground Seat warmer unit control cannot control filament on • Seat warmer control LH malfunction • Seat warmer control RH malfunction • Thermostat (Built-in seat warmer unit LH) malfunction • Thermostat (Built-in seat warmer unit RH) malfunction Seat warmer filament does not generate heat • Seat warmer unit (front seat cushion) malfunction • Seat warmer unit (front seat back) malfunction Seat warmer unit cannot receive operation signal from front climate control unit • Seat warmer control LH malfunction • Seat warmer control RH malfunction • Open circuit or short circuit in wiring harness between the following terminal: ― Seat warmer unit LH terminal 1C—Front climate control unit terminal 1U ― Seat warmer unit RH terminal 1C—Front climate control unit terminal 1S ― Seat warmer unit LH terminal 1D—Front climate control unit terminal 1V ― Seat warmer unit RH terminal 1D—Front climate control unit terminal 1V Front climate control unit cannot receive operation signal from seat warmer unit • Front climate control unit malfunction • Seat warmer switch (Built-in front climate control) malfunction

  Note
  • 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.

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 unit RH. • Switch the ignition to on. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit RH terminal 1E • Is the voltage B+? | Yes | Go to step 6.
No | Go to the next step.
4* | VERIFY IF MALFUNCTION CAUSE IS SHORT CIRCUIT IN SEAT WARMER POWER SUPPLY WIRING HARNESS • Seat warmer unit RH connector is disconnected. • Switch the ignition to off. • Disconnect the seat warmer unit LH connector and BCM connector. • Verify continuity between seat warmer unit wiring harness-side connector terminal 1E and ground. • Is there continuity? | Yes | Repair for a short to ground in the wiring harness.
No | Go to the next step.
5* | VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN SEAT WARMER POWER SUPPLY WITING HARNESS • Seat warmer unit RH, Seat warmer unit LH and BCM connector are disconnected. • Verify the continuity at the following terminal (wiring harness-side): ― Seat warmer unit RH terminal 1E—BCM terminal 6N • Is there continuity? | Yes | • Inspect the BCM 1N and 5L terminal. • Repair the connector or terminals.
No | Repair the wiring harness for open circuit.
6* | DETERMINE IF MALFUNCTION CAUSE IS SIGNAL GROUND WIRING HARNESS OF SEAT WARMER OR MALFUNCTION IN FRONT CLIMATE CONTROL UNIT • Seat warmer unit RH and Seat warmer unit LH connector are disconnected. • Switch the ignition to on. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit LH terminal 1D • Is there voltage 1.0V or less? | Yes | Replace the front climate control unit. (See FRONT CLIMATE CONTROL UNIT REMOVAL/INSTALLATION.)
No | Go to the next step.
7* | DETERMINE IF MALFUNCTION CAUSE IS SIGNAL GROUND WIRING HARNESS OF SEAT WARMER OR MALFUNCTION IN FRONT CLIMATE CONTROL UNIT • Seat warmer unit RH and Seat warmer unit LH connector are disconnected. • Switch the ignition to off. • Disconnect the front climate control unit connector. • Inspect for continuity between the following terminals (wiring harness-side): ― Seat warmer unit LH terminal 1D—Front climate control unit terminal 1V • Is there continuity? | Yes | Replace the front climate control unit. (See FRONT CLIMATE CONTROL UNIT REMOVAL/INSTALLATION.)
No | Repair the wiring harness for open circuit.
8 | DETERMINE MALFUNCTIONING SYSTEM • Is the seat warmer (front seat back) only not operating? | Yes | Go to the next step.
No | Go to step 10.
9* | VERIFY IF MALFUNCTION CAUSE IS SEAT BACK OR SEAT CUSHION • Inspect the seat warmer (front seat back). (See Seat Back.) • Is the seat warmer (front seat back) normal? | Yes | Replace the seat warmer unit (front seat cushion) • Vehicles with occupancy sensor ― Front seat cushion pad (See FRONT SEAT CUSHION TRIM REMOVAL/INSTALLATION.) • Vehicles without occupancy sensor ― Seat warmer unit (See SEAT WARMER UNIT REMOVAL/INSTALLATION.)
No | Replace the seat warmer unit (front seat back). (See Seat Back.)
10* | VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN SEAT WARMER POWER SUPPLY WIRING HARNESS • Switch the ignition to off. • Disconnect the seat warmer unit connector on the side that is not operating. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit terminal on the side that is not operating 1A • Is the voltage B+? | Yes | Go to the next step.
No | • Repair the open circuit in wiring harness between the following terminals: ― S.WARM 15 A fuse—Seat warmer unit 1A
11* | VERIFY IF MALFUNCTION CAUSE IS SHORT TO GROUND IN SEAT WARMER • Disconnect the seat warmer unit connector on the side that is not operating. • Verify continuity between seat warmer unit on the side that is not operating wiring harness-side connector terminal 1B and ground. • Is there continuity? | Yes | • Drive-side seat warmer does not operate. ― Go to the next step. • Passenger-side seat warmer does not operate. ― Go to next step 13.
No | • Inspect the open circuit following. ― Seat warmer unit 1B terminal—GND • Inspect the GND connector terminals for poor connection. • Repair the malfunction.
12* | VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN SEAT WARMER CONTROL POWER SUPPLY WIRING HARNESS • Seat warmer unit LH connector is disconnected. • Switch the ignition to on. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit LH terminal 1E • Is the voltage B+? | Yes | Go to step 14.
No | • Repair the open circuit at the following wiring harness. ― BCM terminal 6N—Seat warmer unit 1E
13* | VERIFY IF MALFANCTION CAUSE IS OPEN CIRCUIT IN SIGNAL GROUND WIRING HARNESS OF SEAT WARMER UNIT RH • Seat warmer unit RH connector is disconnected. • Switch the ignition to on. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit RH terminal 1E • Is there voltage 1.0V or less? | Yes | Go to the next step.
No | • Repair the open circuit at the following wiring harness. ― Front climate control unit terminal 1V—Seat warmer unit RH 1D
14* | VERIFY IF MALFUNCTION CAUSE IS CONTROL SIGNAL SYSTEM OF SEAT WARMER OR MALFUNCTION IN SEAT WARMER UNIT • Seat warmer unit connector on the side that is not operating. • Switch the ignition to on. • Turn the seat warmer switch to LO or HI. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit terminal on the side that is not operating 1C • 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 the next step.
No | Replace the seat warmer unit (front seat cushion) • Vehicles with occupancy sensor ― Front seat cushion pad (See FRONT SEAT CUSHION TRIM REMOVAL/INSTALLATION.) • Vehicles without occupancy sensor ― Seat warmer unit (See SEAT WARMER UNIT REMOVAL/INSTALLATION.)
15* | VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN WIRING HARNESS OF SEAT WARMER CONTROL SIGNAL • seat warmer unit connector on the side that is not operating is disconnected. • Switch the ignition to on. • Disconnect the seat warmer unit connector on the side that is operating and front climate control unit connector. • Verify the continuity at the following terminal (wiring harness-side): ― Drive-side seat warmer does not operate: • Seat warmer unit terminal on the side that is not operating 1C—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—front climate control unit connector 1S • Is there continuity? | Yes | Go to the next step.
No | Repair the open circuit in wiring harness.
16* | VERIFY IF MALFUNCTION CAUSE IS SHORT CIRCUIT IN WIRING HARNESS OF SEAT WARMER CONTROL SIGNAL • Seat warmer units on both sides and front climate control unit connector are disconnected. • Switch the ignition to on. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit terminal on the side that is not operating 1C • Is the voltage B+? | Yes | Repair for a power supply in the wiring harness.
No | Replace the front climate control unit. (See FRONT CLIMATE CONTROL UNIT REMOVAL/INSTALLATION.)

Inspection procedure (No.2 Seat warmer always operations)

No.2 | Seat warmer always operations
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DETECTION | Seat warmer warms seat even though seat warmer switch is off
POSSIBLE CAUSE | Front climate control unit sends operation signal constantly • Front climate control unit malfunction • Seat warmer switch (Built-in front climate control unit) malfunction Seat warmer unit falsely detects that operation signal is ON • Seat warmer unit control LH malfunction • Seat warmer unit control RH malfunction • Open circuit in wiring harness between the following terminal: ― Seat warmer unit LH terminal 1C—Front climate control unit terminal 1U ― Seat warmer unit RH terminal 1C—Front climate control unit terminal 1S Seat warmer unit is in constant ON control status • Seat warmer unit control LH malfunction • Seat warmer unit control RH malfunction • Open circuit in the seat warmer unit LH Internal circuit • Open circuit in the seat warmer unit RH Internal circuit • Short to ground in the seat warmer (front seat back) LH Internal circuit • Short to ground in the seat warmer (front seat back) RH Internal circuit

  Note
  • 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.

Diagnostic procedure

STEP | INSPECTION | ACTION
--- | --- | ---
1* | DETERMINE IF MALFUNCTION CAUSE IS OPERATION SIGNAL OF SEAT WARMER OR MALFUNCTION IN SEAT WARMER UNIT • Switch the ignition to off. • Disconnect the seat warmer unit connector on the side that is not operating. • Switch the ignition to on. • Turn the seat warmer switch to OFF. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit RH terminal 1C • Is the voltage B+? | Yes | Go to step 4.
No | Go to the next step.
2* | VERIFY IF MALFUNCTION CAUSE IS SHORT CIRCUIT IN WIRING HARNESS OF SEAT WARMER OPERATION SIGNAL • Seat warmer unit connector on the side that is not operating is disconnecting. • Switch the ignition to off. • Disconnect the front climate control unit connector. • Verify continuity between seat warmer unit on the side that is not operating wiring harness-side connector terminal 1C and ground. • Is there continuity? | Yes | Repair for a short to ground in the wiring harness.
No | Go to the next step.
3* | VERIFY IF MALFUNCTION CAUSE IS SHORT CIRCUIT FROM OPERATION SIGNAL WIRING HARNESS OF SEAT WARMER TO OTHER WIRING HARNESS OR MALFUNCTION IN FRONT CLIMATE CONTROL UNIT • Seat warmer unit connector on the side that is not operating and front climate control unit connector is disconnected. • Switch the ignition to on. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit terminal on the side that is not operating 1C—GND • Is there any voltage? | Yes | Repair for a short to ground in the wiring harness and other wiring harnesses.
No | Replace the front climate control unit. (See FRONT CLIMATE CONTROL UNIT REMOVAL/INSTALLATION.)
4* | VERIFY IF MALFUNCTION CAUSE IS SHORT TO GROUND IN INTERNAL CIRCUIT OF SEAT WARMER UNIT (FRONT SEAT BACK) HARNESS OR MALFUNCTION IN SEAT WARMER UNIT (FRONT SEAT CUSHION) • Seat warmer unit connector on the side that is not operating is disconnected. • Switch the ignition to off. • Disconnect the seat warmer unit (front seat back) connector on the side that is not operating. (See SEAT WARMER UNIT REMOVAL/INSTALLATION.) • Verify the continuity at the following terminal (wiring harness-side): ― Seat warmer unit (front seat back) terminal on the side that is not operating B—GND • Is there continuity? | Yes | Replace the seat warmer unit (front seat back). (See Seat Back.)
No | Replace the seat warmer unit (front seat cushion) • Vehicles with occupancy sensor ― Front seat cushion pad (See FRONT SEAT CUSHION TRIM REMOVAL/INSTALLATION.) • Vehicles without occupancy sensor ― Seat warmer unit (See SEAT WARMER UNIT REMOVAL/INSTALLATION.)

Inspection procedure (No.3 Temperature of seat warmer cannot be adjusted)

No.3 | Temperature of seat warmer cannot be adjusted
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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 | Front climate control unit sends false signal • Front climate control unit malfunction (Short to ground in the front climate control unit Internal circuit) Seat warmer unit falsely detects operation signal • Seat warmer unit LH control malfunction • Seat warmer unit RH control malfunction • Short to ground in wiring harness between the following terminal: ― Seat warmer unit LH terminal 1C—Front climate control unit terminal 1U ― Seat warmer unit RH terminal 1C—Front climate control unit terminal 1S Seat warmer unit control cannot control filament • Seat warmer unit LH control malfunction • Seat warmer unit RH control malfunction • Thermostat (Built-in seat warmer LH unit) malfunction • Thermostat (Built-in seat warmer RH unit) malfunction • Short to ground in the seat warmer unit LH Internal circuit • Short to ground in the seat warmer unit RH Internal circuit • Short to ground in the seat warmer (front seat back) LH Internal circuit • Short to ground in the seat warmer (front seat back) RH Internal circuit

  Note
  • 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.

Diagnostic procedure

STEP | INSPECTION | ACTION
--- | --- | ---
1* | DETERMINE IF MALFUNCTION CAUSE IS OPERATION SIGNAL OF SEAT WARMER OR MALFUNCTION IN SEAT WARMER UNIT • Switch the ignition to off. • Disconnect the seat warmer unit connector on the side that is not operating. • Switch the ignition to on. • Turn the seat warmer switch to OFF. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit RH terminal 1C • Is the voltage 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 4.
No | Go to the next step.
2* | VERIFY IF MALFUNCTION CAUSE IS SHORT CIRCUIT IN WIRING HARNESS OF SEAT WARMER OPERATION SIGNAL • Seat warmer unit connector on the side that is not operating is disconnected. • Switch the ignition to off • Disconnect the front climate control unit connector. • Verify the continuity at the following terminal (wiring harness-side): ― Seat warmer unit terminal on the side that is not operating 1C—GND • Is there continuity? | Yes | Repair for a short to ground in the wiring harness.
No | Go to the next step.
3* | VERIFY IF MALFUNCTION CAUSE IS SHORT CIRCUIT FROM OPERATION SIGNAL WIRING HARNESS OF SEAT WARMER TO OTHER WIRING HARNESS OR MALFUNCTION IN FRONT CLIMATE CONTROL UNIT • Seat warmer unit connector on the side that is not operating and front climate control unit connector is disconnected. • Switch the ignition to on. • Measure the voltage at the following terminal (wiring harness-side): ― Seat warmer unit terminal on the side that is not operating 1C—GND • Is there any voltage? | Yes | Repair for a short to ground in the wiring harness and other wiring harnesses.
No | Replace the front climate control unit. (See FRONT CLIMATE CONTROL UNIT REMOVAL/INSTALLATION.)
4* | VERIFY IF MALFUNCTION CAUSE IS SHORT TO GROUND IN INTERNAL CIRCUIT OF SEAT WARMER (FRONT SEAT BACK) HARNESS OR MALFUNCTION IN SEAT WARMER UNIT (FRONT SEAT CUSHION) • Seat warmer unit connector on the side that is not operating is disconnected. • Switch the ignition to off. • Disconnect the seat warmer unit (front seat back) connector on the side that is not operating. (See SEAT WARMER UNIT REMOVAL/INSTALLATION.) • Verify the continuity at the following terminal (wiring harness-side): ― Seat warmer unit (front seat back) terminal on the side that is not operating B—GND • Is there continuity? | Yes | Replace the seat warmer unit (front seat back). (See Seat Back.)
No | Replace the seat warmer unit (front seat cushion) • Vehicles with occupancy sensor ― Front seat cushion pad (See FRONT SEAT CUSHION TRIM REMOVAL/INSTALLATION.) • Vehicles without occupancy sensor ― Seat warmer unit (See SEAT WARMER UNIT REMOVAL/INSTALLATION.)

Seat Back

1. Remove the front seat. (See FRONT SEAT REMOVAL/INSTALLATION.)

2. Remove the seat back trim.

3. Verify that the continuity between terminals A and B is as indicated in the table.

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  • If not as indicated in the table, replace the seat warmer unit.

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