DTC Troubleshooting: B121D (89)
DTC B121D or DTC indicator 89: Humidity/In-Car Temperature Sensor Communication Error
DTC Description
DTC
B121D Humidity/In-Car Temperature Sensor Communication Error
  

1.
Problem verification:

Problem verification
?1.
Clear the DTC with the HDS.


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

?3.
Do the Self-Diagnostic Function with the HDS or the climate control unit.

?4.
Check for DTCs.
DTC Description
DTC
B121D Humidity/in-car temperature sensor communication error
  

Is DTC B121D or 89 indicated?

     
YES
     
     
     
Go to step 2.
     
NO
     
     
     
Intermittent failure. Check for loose wires or poor connections on the humidity/in-car temperature circuit.?
2.
Climate control unit check 1:

Climate control unit check 1
?1.
Turn the vehicle to the OFF (LOCK) mode and then the ON mode.

?2.
Touch and hold the ON/OFF icon, then within 10 seconds touch and release the MODE icon five times.


Is the MODE icon off?

     
YES
     
     
     
Go to step 3.
     
NO
     
     
     
Go to step 6.
3.
Climate control unit check 2:

Climate control unit check 2
?1.
Disconnect the following connector.
Humidity/in-car temperature sensor 4P connector

?2.
Connect terminals A and B with a jumper wire.
Terminal A
Humidity/in-car temperature sensor 4P connector No. 2
Terminal B
Humidity/in-car temperature sensor 4P connector No. 4


?3.
Turn the vehicle to the ON mode.

?4.
Touch and hold the ON/OFF icon, then within 10 seconds touch and release the MODE icon five times.


Does the MODE icon turn on?

     
YES
     
     
     
Go to step 4.
     
NO
     
     
     
Go to step 8.
4.
Determine possible failure area (S 5V line, others):

Determine possible failure area (S 5V line, others)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the jumper wire.

?3.
Turn the vehicle to the ON mode.

?4.
Measure the voltage between test points 1 and 2.
Test condition
Vehicle ON mode
Humidity/in-car temperature sensor 4P connector: disconnected
Test point 1
Humidity/in-car temperature sensor 4P connector No. 1
Test point 2
Body ground


Is there about 5 V?

     
YES
     
     
     
Go to step 5.
     
NO
     
     
     
Go to step 12.
5.
Open wire check (SENSOR COM line):

Open wire check (SENSOR COM line)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Climate control unit 32P connector

?3.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Climate control unit 32P connector: disconnected
Humidity/in-car temperature sensor 4P connector: disconnected
Test point 1
Climate control unit 32P connector No. 30
Test point 2
Humidity/in-car temperature sensor 4P connector No. 3


Is there continuity?

     
YES
     
     
     
     
NO
     
     
     
Repair an open in the wire between the climate control unit and the humidity/in-car temperature sensor.?
6.
Determine possible failure area (humidity/in-car temperature sensor, others):

Determine possible failure area (humidity/in-car temperature sensor, others)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Humidity/in-car temperature sensor 4P connector

?3.
Turn the vehicle to the ON mode.

?4.
Touch and hold the ON/OFF icon, then within 10 seconds touch and release the MODE icon five times.


Does the MODE icon turn on?

     
YES
     
     
     
Go to step 7.
     
NO
     
     
     
7.
Shorted wire check (HUM DATA line to HUM CLK line):

Shorted wire check (HUM DATA line to HUM CLK line)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Climate control unit 32P connector

?3.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Climate control unit 32P connector: disconnected
Humidity/in-car temperature sensor 4P connector: disconnected
Test point 1
Climate control unit 32P connector No. 25
Test point 2
Climate control unit 32P connector No. 26

Is there continuity?

     
YES
     
     
     
Repair a short in the wires between the climate control unit and the humidity/in-car temperature sensor.?
     
NO
     
     
     
The HUM DATA wire to HUM CLK wire are OK. Replace the climate control unit.?
8.
Open wire check (HUM DATA line):

Open wire check (HUM DATA line)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Climate control unit 32P connector

?3.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Climate control unit 32P connector: disconnected
Humidity/in-car temperature sensor 4P connector: disconnected
Test point 1
Climate control unit 32P connector No. 25
Test point 2
Humidity/in-car temperature sensor 4P connector No. 2


Is there continuity?

     
YES
     
     
     
The HUM DATA wire is not open. Go to step 9.
     
NO
     
     
     
Repair an open in the wire between the climate control unit and the humidity/in-car temperature sensor.?
9.
Open wire check (HUM CLK line):

Open wire check (HUM CLK line)
?1.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Climate control unit 32P connector: disconnected
Humidity/in-car temperature sensor 4P connector: disconnected
Test point 1
Climate control unit 32P connector No. 26
Test point 2
Humidity/in-car temperature sensor 4P connector No. 4


Is there continuity?

     
YES
     
     
     
The HUM CLK wire is not open. Go to step 10.
     
NO
     
     
     
Repair an open in the wire between the climate control unit and the humidity/in-car temperature sensor.?
10.
Shorted wire check (HUM DATA line):

Shorted wire check (HUM DATA line)
?1.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Climate control unit 32P connector: disconnected
Humidity/in-car temperature sensor 4P connector: disconnected
Test point 1
Climate control unit 32P connector No. 25
Test point 2
Body ground

Is there continuity?

     
YES
     
     
     
Repair a short to ground in the wire between the climate control unit and the humidity/in-car temperature sensor.?
     
NO
     
     
     
The HUM DATA wire is not shorted. Go to step 11.
11.
Shorted wire check (HUM CLK line):

Shorted wire check (HUM CLK line)
?1.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Climate control unit 32P connector: disconnected
Humidity/in-car temperature sensor 4P connector: disconnected
Test point 1
Climate control unit 32P connector No. 26
Test point 2
Body ground

Is there continuity?

     
YES
     
     
     
Repair a short to ground in the wire between the climate control unit and the humidity/in-car temperature sensor.?
     
NO
     
     
     
The HUM CLK wire is not shorted. Replace the climate control unit.?
12.
Open wire check (S 5V line):

Open wire check (S 5V line)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Climate control unit 32P connector

?3.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Climate control unit 32P connector: disconnected
Humidity/in-car temperature sensor 4P connector: disconnected
Test point 1
Climate control unit 32P connector No. 24
Test point 2
Humidity/in-car temperature sensor 4P connector No. 1


Is there continuity?

     
YES
     
     
     
The S 5V wire is OK. Replace the climate control unit.?
     
NO
     
     
     
Repair an open in the wire between the climate control unit and the humidity/in-car temperature sensor.?