DTC Troubleshooting: B121A (G and A/C ON)
DTC B121A or DTC indicator G and A/C ON:
An Open in the Mode Control Motor Circuit
  1. Clear the DTC with the HDS.
  1. Turn the ignition switch to LOCK (0) and then to ON (II).
  1. Do the self-diagnostic function with the HDS or the heater control unit.
  1. Check for DTCs.
Is DTC B121A or G and A/C ON indicated?
YES -
Go to Step 5 .
NO -
Intermittent failure; check for loose wires or poor connections on the mode control motor circuit.■
  1. Turn the ignition switch to LOCK (0).
  1. Test the mode control motor.
Is the mode control motor OK?
YES -
Go to Step 7 .
NO -
Replace the mode control motor. ■
  1. Disconnect the mode control motor 7P connector.
  1. Disconnect heater control unit connectors A (28P) and B (12P).
  1. Check for continuity between the following terminals of heater control unit connectors A (28P), B (12P), and the mode control motor 7P connector.
    28P:
    7P:
    No. 11
    No. 3
    No. 10
    No. 7
    No. 12
    No. 5


Is there continuity?
YES -
Check for loose wires or poor connections at heater control unit connectors A (28P), B (12P), and at the mode control motor 7P connector. If the connections are good, substitute a known-good heater control unit and recheck. If the symptom/indication goes away, replace the original heater control unit .■
NO -
Repair open in the wire(s) between the heater control unit and the mode control motor.■