STEP 1. Using scan tool MB991958, check actuator test of A/C controller assembly (A/C-ECU) check.
STEP 2. Check open and short circuit in COOL and HOT line between air mixing damper control motor and potentiometer connector (damper control motor side) and auto A/C controller assembly (A/C-ECU) connector.
STEP 3. Check the air mixing damper control motor and potentiometer.
STEP 4. Check whether the diagnostic trouble code is stored again.