U0617Lost Communication With Engine Coolant Bypass Valve C
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Unlike its LIN-based neighbours, GM uses U0617 for a coolant bypass valve whose position sensor transmits SENT frames (SAE J2716) to the engine controller. The tables 25OBDG03B and 25OBDG04B count a failure when the input hardware flags a message fault, when pulses arrive but the newest frame is older than 6.25 ms, or when the SENT pin voltage stays above or below a controller limit while frames go stale. Four failures within a five-second window set the code as Type B over two trips; the 2019 table 19OBDG03D still ran it as Type A after one trip. Suppliers such as Rheinmetall offer coolant valves with SENT position feedback. Typical causes are wiring and connector faults on the three-wire sensor line. The valve may stop being regulated, so warm-up and heater output can suffer.
- What you may notice
- Check engine light (on GM after two trips, on 2019 calibrations after one)
- Slow warm-up or reduced heater output
- Possibly further coolant valve codes stored at the same time
- Likely causes
- LikelySENT signal, 5 V supply or ground wire of the valve position sensor open or shorted
- PossibleCorroded or loose connector at the valve
- PossiblePosition sensor inside the valve failed (usually replaced with the valve)
- RareSENT input of the engine controller faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.