U063FLost Communication With Engine Coolant Flow Control Valve Position Sensor
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- The coolant flow control valve meters how much coolant passes through the engine, and its position sensor often transmits over SENT, a one-way digital protocol with a frame every few milliseconds. U063F flags the loss of that stream. GM's 2025 diesel tables (25OBDG04B) treat it as a Type B fault, with the MIL on the second trip, when 80 of 100 samples taken every 6.25 ms are bad: the last valid SENT frame is older than 6.25 ms while the line sits steady low or high, SENT frame errors are counted, or the pulse counter stops updating. The powertrain relay must supply more than 11 V and the engine must not be cranking. GM's harness chafing bulletin 21-NA-149 for 2019 to 2022 trucks and SUVs lists U063F among many codes. Analog-type sensor faults are P2B5D to P2B60 and P2B6D.
- What you may notice
- Check engine light after two trips
- Coolant temperature control less precise, slower warm-up or higher temperatures
- Likely causes
- LikelyEngine harness chafed through to the SENT, supply or ground wire (GM 21-NA-149)
- PossibleCorroded or loose connector at the flow control valve
- PossiblePosition sensor electronics in the valve failed (usually replaced with the valve)
- RareSENT input of the engine control module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.