FixVault

DTC U0164-Lost Communication With HVAC Control Module: Notes

WARNING: This page is about a different car, the 2007 Mitsubishi Raider. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Communication Circuit Diagram
G04853335Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

For a complete wiring diagram  , refer to appropriate SYSTEM WIRING DIAGRAMS article.

Possible Causes
CAN B BUS CIRCUITS OPEN OR SHORTED 
DTCS RELATED TO BATTERY VOLTAGE, IGNITION, OR VIN MESSAGES 
FCM NOT CONFIGURED CORRECTLY 
A/C HEATER CONTROL POWER AND GROUND 
A/C HEATER CONTROL 
MODULE THAT SET THIS DTC