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Home >> Honda >> 2014 >> Pilot EX-L, FWD >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Heating/Air Conditioning >> DTC Troubleshooting >> DTC B1234 or DTC indicator 2: A Short in the Air Mix Control Motor Circuit (Front)

DTC B1234 or DTC indicator 2: A Short in the Air Mix Control Motor Circuit (Front)

  1. Clear the DTCs with the HDS.
  2. Turn the ignition switch to LOCK (0) and then back to ON (II).
  3. Do the self-diagnostic function with the HDS (see HOW TO USE THE SELF-DIAGNOSTIC FUNCTION WITH THE HDS  ) or the HVAC control unit (see HOW TO USE THE HVAC CONTROL UNIT SELF-DIAGNOSTIC FUNCTION WITHOUT THE HDS  ).
  4. Check for DTCs.

    Is DTC B1234 or 2 indicated? 

    YES  -Go to step 5.

    NO  -Intermittent failure.

  5. Check for DTCs.

    Are these DTCs also present; B1245 or 7, and/or B2980 or 6? 

    YES  -Go to step  13.

    NO  -Go to step 6.

  6. Turn the ignition switch to LOCK (0).
  7. Test the front air mix control motor (see FRONT AIR MIX CONTROL MOTOR TEST  ).

    Is the front air mix control motor OK? 

    YES  -Go to step 8.

    NO  -Replace the front air mix control motor (see FRONT AIR MIX CONTROL MOTOR REPLACEMENT  ).

  8. Disconnect the front air mix control motor 7P connector.
  9. Disconnect HVAC control unit connector A (24P).
  10. Check for continuity between HVAC control unit connector A (24P) terminal No. 16 and body ground.
    Fig 1: Checking Continuity Between HVAC Control Unit Connector A (24P) Terminal No. 16 And Body Ground
    G08090199Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Repair a short to body ground in the wire between the HVAC control unit and the front air mix control motor.

    NO  -Go to step 11.

  11. Check for continuity between HVAC control unit connector A (24P) terminals No. 14 and No. 16.
    Fig 2: Checking Continuity Between HVAC Control Unit Connector A (24P) Terminals No. 14 And 16
    G08090200Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Repair a short in the wire(s).

    NO  -Go to step 12.

  12. Turn the ignition switch to ON (II), and measure the voltage between HVAC control unit connector A (24P) terminal No. 16 and body ground.
    Fig 3: Measuring Voltage Between HVAC Control Unit Connector A (24P) Terminal No. 16 And Body Ground
    G08090201Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there any voltage? 

    YES  -Repair a short to power in the wire between the HVAC control unit and the front air mix control motor. This short may also damage the HVAC control unit. Repair a short to power before replacing the HVAC control unit.

    NO  -Substitute a known-good HVAC control unit, and recheck. If the symptom/indication goes away, replace the original HVAC control unit (see HVAC CONTROL UNIT REMOVAL/INSTALLATION  ).

  13. Turn the ignition switch to LOCK (0), and disconnect the HVAC control unit.
  14. Disconnect these items:
    • Front air mix control motor
    • Rear air mix control motor
    • A/C pressure sensor
  15. Check for continuity between HVAC control unit connector A (24P) terminal No. 14 and body ground.
    Fig 4: Checking Continuity Between HVAC Control Unit Connector A (24P) Terminal No. 14 And Body Ground
    G08090202Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Repair a short to body ground in the wire.

    NO  -Go to step 16.

  16. Turn the ignition switch to ON (II), and check the same terminal for voltage to body ground.
    Fig 5: Checking Terminal For Voltage To Body Ground
    G08090203Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there any voltage? 

    YES  -Repair a short to power in the wire. This short may have also damaged the HVAC control unit. Repair a short to power before replacing the HVAC control unit.

    NO  -Go to step 17.

  17. Turn the ignition switch to LOCK (0).
  18. Reconnect the HVAC control unit connector A (24P).
  19. Turn the ignition switch to ON (II), and measure the voltage between HVAC control unit connector A (24P) terminal No. 14 and body ground.
    Fig 6: Measuring Voltage Between HVAC Control Unit Connector A (24P) Terminal No. 14 And Body Ground
    G08090204Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there about 5 V? 

    YES  -Go to step 20.

    NO  -Check for a loose wire or poor connection at HVAC control unit connector A (24P). If the connection is good, substitute a known-good HVAC control unit and recheck. If the symptom/indication goes away, replace the original HVAC control unit (see HVAC CONTROL UNIT REMOVAL/INSTALLATION  ).

  20. While checking the same terminal for voltage to ground, reconnect these items individually and note the voltage reading each time:
    • Front air mix control motor
    • Rear air mix control motor
    • A/C pressure sensor
      Fig 7: Checking HVAC Control Unit Connector A (24P) Terminal For Voltage To Ground
      G08090205Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Does the voltage remain at about 5 V? 

    YES  -Substitute a known-good HVAC control unit and recheck. If the symptom/indication goes away, replace the original HVAC control unit (see HVAC CONTROL UNIT REMOVAL/INSTALLATION  ).

    NO  -Replace the component that caused the voltage drop.

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