DTC Troubleshooting: B1237 (E and A/C ON)
  1. Turn the ignition switch to ON (II), and check the same terminal for voltage to body ground.
Is there any voltage?
YES -
Repair short to power in the wire. This short may have also damaged the heater control unit. Repair short to power before replacing the heater control unit.■
NO -
Go to Step 17 .
  1. Turn the ignition switch to LOCK (0).
  1. Reconnect heater control unit connector B (12P).