U063A: Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor C

What it means

A control module has stopped receiving expected network messages from hybrid/EV electronics coolant temperature sensor C. The effect on electronics thermal management depends on the vehicle's system design.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

Hybrid/EV electronics coolant temperature sensor C reports the coolant temperature used to protect high-voltage electronics. Its readings travel over the vehicle network to modules that manage cooling. U063A sets when a module stops receiving expected messages from sensor C, leaving that temperature input unavailable.

Common causes

Most likely first.

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

Symptoms

• Warning light or message related to the affected system
• Coolant temperature data may be unavailable

How to diagnose it

1. Scan all modules for related communication codes and review freeze-frame data to identify when sensor C stopped reporting.
2. Check live data for electronics coolant temperature sensor C and compare it with other available temperature readings for a missing or stale value.
3. Inspect sensor C’s network wiring and connectors for looseness, corrosion, chafing, or damage, using the wiring information to locate the correct branch.
4. Check power and ground at the sensor or its reporting module against the manufacturer’s specification.
5. Test the network circuit for opens or shorts, then assess whether the sensor C reporting module has failed.

Common fixes

• Reconnect or repair a loose or damaged sensor C network connector.
• Repair an open or short in the network wiring to sensor C.
• Restore the sensor or its module’s power or ground supply.
• Replace the failed sensor C reporting module if circuit tests confirm an internal failure.

Can I keep driving?

Avoid demanding driving if a hybrid/EV temperature warning appears or the vehicle limits power, because electronics cooling may be affected and reduced-power operation may follow. Stop safely if a temperature warning comes on, and have the fault diagnosed before continued use.