U0628: Lost Communication With A/C Refrigerant Pressure Sensor B

What it means

A control module has stopped receiving expected network messages from A/C refrigerant pressure sensor B. The effect on A/C operation depends on the vehicle's system design.

How it works

A/C refrigerant pressure sensor B supplies pressure information over the vehicle network. The receiving module expects regular messages from sensor B, and U0628 sets when those messages stop. The A/C controls may restrict operation if they cannot use the pressure reading.

Common causes

Most likely first.

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

Symptoms

• A/C may not operate as intended
• Warning light or message related to the A/C system

How to diagnose it

1. Scan all modules and save available event data to determine whether sensor B communication loss is isolated or accompanied by other network faults.
2. Check live A/C data for pressure sensor B and compare its availability with pressure sensor A, if that data is supported.
3. Inspect sensor B's connector and nearby network wiring for corrosion, loose pins, chafing, or physical damage.
4. Check the sensor module's power and ground against the manufacturer's specification.
5. Test the bus wiring serving pressure sensor B for opens or shorts using the vehicle wiring diagram and manufacturer's procedure.

Common fixes

• Clean and secure sensor B's connector or repair damaged wiring.
• Restore the sensor module's power or ground.
• Repair an open or short in the communication wiring to pressure sensor B.
• Replace the sensor module if it remains offline after its power, ground, and wiring are verified.

Can I keep driving?

The vehicle is generally drivable, though the A/C may cool poorly or shut off. Do not rely on it for demisting until operation is restored.