DTC B121D (89): Humidity/In-Car Temperature Sensor Communication Error
NOTE: If other short circuit DTCs are indicated at the same time, there may be an open or short to body ground in the power (5 V) circuit.
| DTC Description | DTC |
|---|---|
| B121D Humidity/in-car temperature sensor communication error |
- 1. 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 - Refer to: How to Troubleshoot the Body ElectricalHow to Troubleshoot the Climate Control System .
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 sensor circuit.
- 2. Humidity/in-car temperature sensor SENSOR 5V line check:
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. 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 3.
NO
Go to step 7.
- 3. 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. 23 Test point 2 Humidity/in-car temperature sensor 4P connector No. 3 Is there continuity?
YES
The SENSOR COM wire is OK. Go to step 4.
NO
Repair an open in the wire between the climate control unit and the humidity/in-car temperature sensor.
- 4. Climate control unit HUM CLK, HUM DATA lines check 1:
1. 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 2. 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 Humidity/in-car temperature sensor 4P connector No. 2 and No. 4: jumped Test point 1 Climate control unit 32P connector No. 4 Test point 2 Climate control unit 32P connector No. 5 Is there continuity?
YES
Go to step 5.
NO
Go to step 8.
- 5. Climate control unit HUM CLK, HUM DATA lines check 2:
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 Humidity/in-car temperature sensor 4P connector No. 2 and No. 4: jumped Test point 1 Climate control unit 32P connector No. 4 Test point 2 Body ground Is there continuity?
YES
Go to step 6.
NO
Go to step 9.
- 6. Shorted wire check (HUM DATA line):
1. Disconnect the jumper wire.
2. 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. 4 Test point 2 Body ground Is there continuity?
YES
Repair a short to ground in the HUM DATA wire between the climate control unit and the humidity/in-car temperature sensor.
NO
Repair a short to ground in the HUM CLK wire between the climate control unit and the humidity/in-car temperature sensor.
- 7. Open wire check (SENSOR 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. 17 Test point 2 Humidity/in-car temperature sensor 4P connector No. 1 Is there continuity?
YES
Replace the climate control unit .
NO
Repair an open in the wire between the climate control unit and the humidity/in-car temperature sensor.
- 8. Open wire check (HUM DATA line):
1. Disconnect the jumper wire.
2. 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. 4 Test point 2 Humidity/in-car temperature sensor 4P connector No. 2 Is there continuity?
YES
Repair an open in the HUM CLK wire between the climate control unit and the humidity/in-car temperature sensor.
NO
Repair an open in the HUM DATA wire between the climate control unit and the humidity/in-car temperature sensor.
- 9. Shorted wire check (HUM CLK line to HUM DATA line):
1. Disconnect the jumper wire.
2. 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. 4 Test point 2 Climate control unit 32P connector No. 5 Is there continuity?
YES
Repair a short in the wires between the climate control unit and the humidity/in-car temperature sensor.
NO
Go to step 10.
- 10. Climate control unit check:
1. Reconnect the climate control unit 32P 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. Press and hold the AUTO and ON/OFF buttons.
Does the mode indicator turn on?
YES
Replace the humidity/in-car temperature sensor .
NO
