U0164 is set when the vehicle network detects a loss of communication with the HVAC control module. The powertrain control module (PCM) records this code because it cannot receive messages from the HVAC module, typically due to a module, power, ground, or wiring problem rather than a failure of the PCM itself. As a result, the climate‑control system may become inoperative or operate in a limited manual mode.
The module itself can fail, preventing it from transmitting on the CAN bus. This is the most common reason for a loss‑of‑communication code.
A blown fuse, faulty relay, or wiring problem can cut voltage to the module, causing it to drop off the network.
Corroded, loose, or broken ground at the HVAC module can prevent proper operation and communication.
Breaks, shorts, or corrosion in the CAN high/low wires between the HVAC module and the network interrupt data exchange.
A poor connection at the module harness can interrupt both power and the CAN bus signals.
Rarely, the PCM itself fails to receive messages; however, this is usually a consequence of the HVAC module being offline, not the root cause.
No. While the PCM logs the code because it cannot receive messages, the problem is almost always the HVAC module, its power/ground supply, or the CAN wiring. Replacing the PCM rarely fixes this code.
Yes. If the fuse that supplies voltage to the HVAC module blows, the module loses power and drops off the bus, setting U0164.
The engine and transmission will continue to operate normally, but the climate‑control system may be unresponsive or default to a manual mode.
Yes. A short or open on the CAN network can affect many modules, so you may see several U‑codes in addition to U0164.