U063F: Lost Communication With Engine Coolant Flow Control Valve Position Sensor

What it means

A control module has stopped receiving expected network messages from the engine coolant flow control valve position sensor. The effect on coolant flow control depends on the vehicle's system design.

At a glance

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

How it works

The engine coolant flow control valve position sensor reports where the valve is positioned so the control module can manage coolant circulation. The module expects those status messages over the vehicle network. U063F sets when messages from this position sensor are lost, leaving the module unable to confirm the valve’s position and coolant flow control.

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 flow control may be affected

How to diagnose it

1. Scan all modules and review freeze-frame data for communication faults recorded with the coolant flow control valve position sensor loss.
2. Check live data for the valve position reading and compare commanded and reported positions if both are available.
3. Inspect the position sensor’s network wiring and connector for damage, corrosion, loose terminals, or coolant contamination.
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 evaluate the sensor reporting module if wiring and supplies are intact.

Common fixes

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

Can I keep driving?

If the engine temperature warning appears or the temperature gauge rises, stop safely because the system may not be controlling coolant flow correctly. Until diagnosed, avoid heavy loads and extended trips.