U063F

Code

Generic U — Network/User

Lost Communication With Engine Coolant Flow Control Valve Position Sensor

Brand: Generic

Type: U — Network/User

Views: UK: 32 EN: 74 RU: 33

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Page language: EN

Open/short in the sensor/module wiring or CAN bus
Disconnected, corroded or damaged connector at the valve position sensor or nearby harness
Blown fuse or loss of sensor/module power or ground
Failed engine coolant flow control valve position sensor or integrated actuator module
Faulty or intermittent CAN/LIN network (missing termination, short to supply or ground)
Fault in the controlling ECU/PCM or other module that relays the data

Malfunction Indicator Lamp (MIL) or network warning illuminated
Diagnostic trouble code stored related to coolant control or communications
Reduced or improper coolant flow control (reduced heating/temperature control) — may be intermittent
Cooling system or climate control behavior abnormal
Possible drivability complaints if cooling control impacts engine operation

Read and record U063F and any other stored codes and freeze-frame data with a scan tool
Check battery voltage and charging system (low voltage can cause network errors)
Visually inspect the sensor connector and wiring for corrosion, damage, pin push-out or water intrusion
Verify sensor/module supply voltage and ground at the connector
Check CAN bus physical layer: measure CAN H and CAN L voltages and differential with key on, engine off
Check for proper termination resistors (≈120 ohm each end; approx. 60 ohm across CAN H-L)

Sensor supply: typically ignition-switched 5V or vehicle battery depending on design (verify with wiring diagram)
Position output (if analog potentiometer): approximate 0.5–4.5 VDC across travel (varies by manufacturer)
Position output (if digital/Hall): pulsed or CAN message containing position; check for serial/CAN traffic
CAN bus idle voltages: CAN H ≈ 2.5–3.0 V, CAN L ≈ 2.5–1.5 V; differential ≈ 0 V idle, ≈2 V dominant
Expected update rate: periodic messages/packets at a rate defined by manufacturer (use OEM data or scope/scan tool to confirm)

Capture codes and freeze-frame; note any other U- or P-codes that may indicate network or power faults.
Visually inspect harness and connector at the coolant flow control valve and trace the wiring back for damage or repairs.
Verify power and ground at the sensor/module connector with key ON. If missing, trace and repair supply/ground issue.
Check CAN bus health: measure CAN H and CAN L voltages and differential. If abnormal, isolate sections of the bus and inspect for shorts or missing termination.
Use a scan tool to watch live data for the valve position. Attempt to command the valve (bi-directional control) if available and observe response.
Perform continuity and resistance checks between the sensor connector and the controlling module connector; repair any opens or high resistance.
If wiring and bus are good but no communication, replace the coolant flow control valve position sensor/module and re-test.
If replacing module, verify correct programming/configuration and clear codes. Re-check for recurrence and perform final network checks.
If code persists after sensor replacement, suspect receiving ECU/module or intermittent wiring fault; consult manufacturer diagnostics for module-level testing.

Damaged connector or wiring to the coolant flow control valve position sensor (water intrusion, chafing)
Sensor/module internal failure (no transmit or corrupted output)
Loss of sensor supply voltage or ground
CAN bus fault between sensor module and receiving module (open, short, high resistance)
Module programming/mismatch after replacement