Various HVAC Concerns And DTCs - keywords B0228 B0413 B0423 B3779 blow blower cold DTC hot mode temperature warm

This PI was superseded to remove the engineering contact information. Please discard PIT4471A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Owners may comment on various HVAC concerns and DTCs B0228, B0413, B0423, and/or B3779 may be set. Also, complaints of the temperature door defaulting to the full hot or cold positions or the mode door defaulting to the defrost position.

Check the following areas:

1. Right I/P junction block (Document ID # 1562972) connectors C4/X4 & C5/X5 for poor terminal tension, backed out terminals or connectors not fully seated.
2. Check the actuator connectors for poor terminal tension, backed out terminals or connectors not fully seated.
3. Check for a damaged HVAC harness in the area shown in the picture below.

If no wiring issues are found and there is still a concern with an HVAC actuator, before replacing the actuator perform a reset of the front HVAC control head. To perform a reset remove the "HVAC BATT" fuse for one minute and reinstall. After the fuse has been reinstalled start the engine and allow it to run for one minute without using the hvac controls. After one minute use the Tech 2 to perform a door relearn procedure by entering Body/ HVAC Control Module/ Special Functions/ Recalibrate All Motors. If the actuator begins to operate, no further repairs necessary. If the actuator still does not operate perform normal diagnostics, by first checking for any new DTCs.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.