DTC B121B (4A): A Short in the Mode Control Motor Circuit

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.

• 1. Problem verification:

  1. Clear the DTCs 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
  B121B A short in the mode control motor circuit

  Is DTC B121B or 4A indicated?

  YES 

  Go to step 2.

  NO 

  Intermittent failure. Check for loose wires or poor connections on the mode control motor circuit.

• 2. Determine possible failure area (SENSOR 5V/S5V line, others):

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

  2. Disconnect the following connector.

  Mode control motor 7P connector

  3. Turn the vehicle to the ON mode.

  4. Measure the voltage between test points 1 and 2.

  Test condition	Vehicle ON mode
  	Mode control motor 7P connector: disconnected
  Test point 1	Mode control motor 7P connector No. 1
  Test point 2	Body ground

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

  Is there about 5 V?

  YES 

  The SENSOR 5V/S5V wire is OK. Go to step 3.

  NO 

  Go to step 4.

• 3. Determine possible failure area (mode control motor, others):

  1. Measure the voltage between test points 1 and 2.

  Test condition	Vehicle ON mode
  	Mode control motor 7P connector: disconnected
  Test point 1	Mode control motor 7P connector No. 2
  Test point 2	Body ground

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

  Is there about 5 V?

  YES 

  Replace the mode control motor .

  NO 

  Go to step 6.

• 4. Open wire check (SENSOR 5V/S5V line):

  1. Measure the voltage between test points 1 and 2.

  Test condition	Vehicle ON mode
  	Mode control motor 7P connector: disconnected
  Test point 1	Climate control unit 32P connector No. 17
  Test point 2	Body ground

  Is there about 5 V?

  YES 

  Repair an open in the wire between the climate control unit and the mode control motor.

  NO 

  Go to step 5.

• 5. Shorted wire check (SENSOR 5V/S5V 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
  	Mode control motor 7P connector: disconnected
  Test point 1	Climate control unit 32P connector No. 17
  Test point 2	Body ground

  Is there continuity?

  YES 

  Repair a short to ground in the wire between the climate control unit and the mode control motor.

  NO 

  The SENSOR 5V/S5V wire is OK. Replace the climate control unit .

• 6. Shorted wire check (MODE-P 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
  	Mode control motor 7P connector: disconnected
  Test point 1	Climate control unit 32P connector No. 22
  Test point 2	Body ground

  Is there continuity?

  YES 

  Repair a short to ground in the wire between the climate control unit and the mode control motor.

  NO 

  The MODE-P wire is OK. Replace the climate control unit .