DTC Troubleshooting: B1228 (D and AUTO)
  1. Check for continuity between heater control unit connector A (28P) No. 24 terminal and heater control unit connector B (12P) No. 10 terminal.
Is there continuity?
YES -
Repair short in the wires between the heater control unit and the outside air temperature sensor.■
NO -
Substitute a known-good heater control unit, and recheck. If the symptom/indication goes away, replace the original heater control unit .■