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DTC B121D (89)

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DTC B121D or DTC indicator 89  : Humidity/in-car temperature sensor communication error

DTC Description DTC
B121D Humidity/in-car temperature sensor communication error  

DTC (AC)

  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 .

    -4. Check for DTCs.

    DTC Description DTC
    B121D Humidity/in-car temperature sensor communication error  

    Is DTC B121D or 89 indicated?

    YES 

    The failure is duplicated. Go to step 2.

    NO 

    Intermittent failure. Check for loose wires or poor connections on the humidity/in-car temperature sensor circuit.

  2. Climate control unit check 1

    -1. Turn the vehicle to the OFF (LOCK) mode after confirming the A/C system is OFF.

    -2. Disconnect the following connector.

    Humidity/in-car temperature sensor 4P connector

    -3. Turn the vehicle to the ON mode.

    -4. While pressing the WINDSHIELD DEFROST button, press and hold the ON/OFF button for 10 seconds or more.

    GHH395981Courtesy of HONDA, U.S.A., INC.

    Does the MODE indicator turn on?

    YES 

    Go to step 5.

    NO 

    Go to step 3.

  3. Climate control unit check 2

    -1. Turn the vehicle to the OFF (LOCK) mode after confirming the A/C system is OFF.

    -2. Connect terminals A and B with a jumper wire.

    Terminal A Humidity/in-car temperature sensor 4P connector (female terminals) No. 2:
    Terminal B Humidity/in-car temperature sensor 4P connector (female terminals) No. 4:
    GHH395984Courtesy of HONDA, U.S.A., INC.

    -3. Turn the vehicle to the ON mode.

    -4. While pressing the WINDSHIELD DEFROST button, press and hold the ON/OFF button for 10 seconds or more.

    GHH395985Courtesy of HONDA, U.S.A., INC.

    Does the MODE indicator turn on?

    YES 

    Go to step 4.

    NO 

    Go to step 6.

  4. Determine possible failure area (humidity/in-car temperature sensor, 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 (female terminals) No. 1:
    Test point 2 Body ground
    GHH395987Courtesy of HONDA, U.S.A., INC.

    Is there about 5 V?

    YES 

    Replace the humidity/in-car temperature sensor .

    NO 

    Go to step 10.

  5. 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 connector A (32P)

    -3. Check for continuity between test points 1 and 2.

    Test condition Vehicle OFF (LOCK) mode
    Climate control unit connector A (32P): disconnected
    Humidity/in-car temperature sensor 4P connector: disconnected
    Test point 1 Climate control unit connector A (32P) No. 7
    Test point 2 Climate control unit connector A (32P) No. 24

    Is there continuity?

    YES 

    Repair a short in the HUM DATA wire to the HUM CLK wire.

    NO 

    Replace the climate control unit .

  6. Open wire check (HUM DATA line)

    -1. Turn the vehicle to the OFF (LOCK) mode.

    -2. Disconnect the jumper wire.

    -3. Disconnect the following connector.

    Climate control unit connector A (32P)

    -4. Check for continuity between test points 1 and 2.

    Test condition Vehicle OFF (LOCK) mode
    Climate control unit connector A (32P): disconnected
    Humidity/in-car temperature sensor 4P connector: disconnected
    Test point 1 Climate control unit connector A (32P) No. 7
    Test point 2 Humidity/in-car temperature sensor 4P connector (female terminals) No. 2:
    GHH395989Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The HUM DATA wire is not open. Go to step 7.

    NO 

    Repair an open in the HUM DATA wire.

  7. 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 connector A (32P): disconnected
    Humidity/in-car temperature sensor 4P connector: disconnected
    Test point 1 Climate control unit connector A (32P) No. 24
    Test point 2 Humidity/in-car temperature sensor 4P connector (female terminals) No. 4:
    GHH395991Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The HUM CLK wire is not open. Go to step 8.

    NO 

    Repair an open in the HUM CLK wire.

  8. 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 connector A (32P): disconnected
    Humidity/in-car temperature sensor 4P connector: disconnected
    Test point 1 Climate control unit connector A (32P) No. 7
    Test point 2 Body ground

    Is there continuity?

    YES 

    Repair a short to ground in the HUM DATA wire.

    NO 

    The HUM DATA wire is OK. Go to step 9.

  9. 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 connector A (32P): disconnected
    Humidity/in-car temperature sensor 4P connector: disconnected
    Test point 1 Climate control unit connector A (32P) No. 24
    Test point 2 Body ground

    Is there continuity?

    YES 

    Repair a short to ground in the HUM CLK wire.

    NO 

    Replace the climate control unit .

  10. Open wire check (S 5V line)

    -1. Turn the vehicle to the OFF (LOCK) mode.

    -2. Disconnect the following connector.

    Climate control unit connector A (32P)

    -3. Check for continuity between test points 1 and 2.

    Test condition Vehicle OFF (LOCK) mode
    Climate control unit connector A (32P): disconnected
    Humidity/in-car temperature sensor 4P connector: disconnected
    Test point 1 Climate control unit connector A (32P) No. 26
    Test point 2 Humidity/in-car temperature sensor 4P connector (female terminals) No. 1:
    GHH395993Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The S 5V wire is not open. Go to step 11.

    NO 

    Repair an open in the S 5V wire.

  11. Open wire check (SENSOR COM line)

    -1. Check for continuity between test points 1 and 2.

    Test condition Vehicle OFF (LOCK) mode
    Climate control unit connector A (32P): disconnected
    Humidity/in-car temperature sensor 4P connector: disconnected
    Test point 1 Climate control unit connector A (32P) No. 12
    Test point 2 Humidity/in-car temperature sensor 4P connector (female terminals) No. 3:
    GHH395995Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The SENSOR COM wire is OK. Go to step 12.

    NO 

    Repair an open in the SENSOR COM wire.

  12. Shorted wire check (S 5V line)

    -1. Check for continuity between test points 1 and 2.

    Test condition Vehicle OFF (LOCK) mode
    Climate control unit connector A (32P): disconnected
    Humidity/in-car temperature sensor 4P connector: disconnected
    Test point 1 Climate control unit connector A (32P) No. 26
    Test point 2 Body ground

    Is there continuity?

    YES 

    Repair a short to ground in the S 5V wire.

    NO 

    Replace the climate control unit .

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