DTC Troubleshooting: B1C57

DTC B1C57: Passenger's Heater Thermistor Circuit Open

NOTE:

	If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A.
	The front seat heater control unit does not turn on the front seat heater until the seat core temperature is 185 °F (85 °C) or less. Make sure the seat core temperature is below 185 °F (85 °C) before troubleshooting.

DTC Description	DTC
B1C57 Passenger's Heater Thermistor Circuit Open

Problem verification:

Problem verification

?1.	Clear the DTCs with the HDS.

?2.	Turn the vehicle to the OFF (LOCK) mode and then the ON mode.

?3.	Wait for at least 90 seconds.

?4.

Check for DTCs with the HDS.

DTC Description	DTC
B1C57 Passenger's Heater Thermistor Circuit Open

Is DTC B1C57 indicated?


	YES

Go to step 2.


	NO

Intermittent failure, the system is OK at this time. Check for loose or poor connections.?

Seat heater check 1:

Seat heater check 1

?1.

Disconnect the following connector.

Front seat heater control unit 14P connector

?2.

Measure the resistance between test points 1 and 2, refer to the following table.

Test condition	Vehicle OFF (LOCK) mode Front seat heater control unit 14P connector: disconnected
Test point 1	Front seat heater control unit 14P connector No. 12
Test point 2	Front seat heater control unit 14P connector No. 6

Is resistance value within the range?


	YES

Replace the front seat heater control unit.?


	NO

Go to step 3.

Seat heater check 2:

Seat heater check 2

?1.

Disconnect the following connector.

Front passenger's seat cushion heater 4P connector

?2.

Measure the resistance between test points 1 and 2, refer to the following table.

Test condition	Vehicle OFF (LOCK) mode Front seat heater control unit 14P connector: disconnected Front passenger's seat cushion heater 4P connector: disconnected
Test point 1	Front passenger's seat cushion heater 4P connector No. 3
Test point 2	Front passenger's seat cushion heater 4P connector No. 4

Is resistance value within the range?


	YES

Replace the front seat heater control unit.?


	NO: without power seat

Go to step 4.


	NO: with power seat

Go to step 5.

Open wire check (+THERMISTER(AS) line):

Open wire check (+THERMISTER(AS) line)

?1.

Connect terminals A and B with a jumper wire.

Terminal A	Front passenger's seat cushion heater 4P connector No. 3
Terminal B	Body ground

?2.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode Front seat heater control unit 14P connector: disconnected Front passenger's seat cushion heater 4P connector: disconnected Front passenger's seat cushion heater 4P connector: jumped to body ground
Test point 1	Front seat heater control unit 14P connector No. 12
Test point 2	Body ground

Is there continuity?


	YES

Repair an open or high resistance in the -THERMISTER(AS) wire.?


	NO

Repair an open or high resistance in the +THERMISTER(AS) wire.?

Open wire check (AS TH+ line):

Open wire check (AS TH+ line)

?1.

Connect terminals A and B with a jumper wire.

Terminal A	Front passenger's seat cushion heater 4P connector No. 3
Terminal B	Body ground

?2.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode Front seat heater control unit 14P connector: disconnected Front passenger's seat cushion heater 4P connector: disconnected Front passenger's seat cushion heater 4P connector: jumped to body ground
Test point 1	Front seat heater control unit 14P connector No. 12
Test point 2	Body ground

Is there continuity?


	YES

Repair an open or high resistance in the AS TH- wire.?


	NO

Repair an open or high resistance in the AS TH+ wire.?