DTC Troubleshooting: B1238 (F and A/C ON)
  1. Check for continuity between body ground and heater control unit connector A (28P) No. 1 and No. 2 terminals individually.
Is there continuity?
YES -
Repair short to body ground in the wire(s) between the heater control unit and the passenger's air mix control motor.■
NO -
Substitute a known-good heater control unit, and recheck. If the symptom/indication goes away, replace the original heater control unit .■