U0605: Lost Communication With A/C Refrigerant Sensor A

What it means

The vehicle bus reports loss of communication with smart A/C refrigerant sensor A. Pressure or composition feedback for the refrigeration loop is unavailable; A/C may default to off.

How it works

A/C refrigerant sensor A sends refrigerant-system information, such as pressure or composition data, over the vehicle network. U0605 sets when the receiving controller loses communication with that sensor, so the A/C system may disable cooling as a protective response.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Record freeze-frame data and scan the climate and network modules for related refrigerant, compressor, or communication faults.
2. Check whether the A/C is disabled or cooling poorly, and see whether live data for refrigerant sensor A is missing.
3. Inspect the sensor A connector and accessible wiring for corrosion, damage, disconnection, or signs of a recent repair near the refrigerant lines.
4. Check the sensor’s specified power, ground, and network wiring to the manufacturer’s specification, and determine whether other modules on the same network are also offline.
5. If wiring and power are sound, test sensor A communication and verify configuration before considering sensor or controller replacement.

Common fixes

• Reconnect or repair a loose, corroded, or damaged sensor A connector or network wire.
• Restore the sensor’s specified power or ground.
• Repair a shared network fault if other modules also report communication loss.
• Replace A/C refrigerant sensor A if testing confirms it has failed.
• Correct a configuration or controller fault if vehicle-specific diagnosis confirms it.

Can I keep driving?

The fault usually affects A/C operation rather than basic vehicle control, so driving is generally possible if visibility remains clear. Do not drive if poor defogging prevents a clear view, and have the A/C fault diagnosed if the system remains disabled.