DTC Troubleshooting: B121A (B-B4), B121A (49)
DTC B121A or DTC screen B-B4 or DTC indicator 49: An Open in the Mode Control Motor Circuit
DTC Description
DTC
B121A An open in the mode control motor circuit
  

1.
Problem verification:

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.

?4.
Check for DTCs.
DTC Description
DTC
B121A An open in the mode control motor circuit
  

Is DTC B121A, Error on the DTC screen B-B4 (climate control panel without display) or 49 (climate control panel with display) 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 (MDD-P-DR line, others):

Determine possible failure area (MDD-P-DR line, others)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Mode control motor 5P 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 5P connector: disconnected
Test point 1
Mode control motor 5P connector No. 4
Test point 2
Body ground


Is there about 5 V?

     
YES
     
     
     
The MDD-P-DR wire is OK. Go to step 3.
     
NO
     
     
     
Go to step 4.
3.
Open wire check (SENS COM-H line):

Open wire check (SENS COM-H line)
?1.
Measure the voltage between test points 1 and 2.
Test condition
Vehicle ON mode
Mode control motor 5P connector: disconnected
Test point 1
Mode control motor 5P connector No. 4
Test point 2
Mode control motor 5P connector No. 5


Is there about 5 V?

     
YES
     
     
     
     
NO
     
     
     
Repair an open in the SENS COM-H wire.?
4.
Open wire check (MDD-P-DR line):

Open wire check (MDD-P-DR line)
?1.
Measure the voltage between test points 1 and 2.
Test condition
Vehicle ON mode
Mode control motor 5P connector: disconnected
Test point 1
Climate control unit connector B (24P) No. 5
Test point 2
Body ground

Is there about 5 V?

     
YES
     
     
     
Repair an open in the MDD-P-DR wire.?
     
NO