U016B: Lost Communication With A/C Compressor Control Module

What it means

ECU lost CAN communication with the A/C compressor control module (electric A/C compressor on hybrids/EVs).

At a glance

• Usually lights the warning light of the system that lost communication

How it works

The A/C compressor control module manages the electric compressor used in some hybrid and electric vehicles, and exchanges status messages with other modules over the CAN network. U016B sets when the reporting module does not receive the expected messages from that compressor module within the required time.

Common causes

Most likely first.

1. Module unpowered
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

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. Scan all modules for communication codes and note whether U016B is current or stored, since faults in several modules can point to a shared network or power problem.
2. Check freeze-frame data and live module status for when communication stopped, and confirm whether the A/C compressor control module responds to a scan tool.
3. Inspect the compressor module’s power, ground, connectors, and harness for loose connections, corrosion, or damage.
4. Check the relevant fuses and verify module power and ground under the conditions specified by the manufacturer.
5. If power and ground are sound, test the CAN wiring and termination against the manufacturer's specification, then check gateway routing if the network tests pass.

Common fixes

• Restore a poor connection or repair damaged wiring at the compressor module.
• Replace a blown fuse or repair the module’s power or ground supply.
• Repair a CAN network fault or correct a gateway routing issue.
• Replace the A/C compressor control module if its supplies and network connections are confirmed good.

Can I keep driving?

If the vehicle drives normally, a short trip may be possible, but the electric A/C compressor may be unavailable and other warnings can appear. Avoid relying on cabin cooling or heating for visibility or comfort until the fault is diagnosed.