U0615Lost Communication With Engine Coolant Bypass Valve A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Engines with split cooling circuits often route coolant through an electrically driven valve that reports its position and status digitally. U0615 is stored when the engine controller gets no answer from bypass valve A. In GM's 2019 hybrid tables (19OBDG01) the valve sits on a LIN bus: once Run mode and at least 11 V have held for 400 ms, three missed responses fail the test as Type B, and the valve's own position check (P15C5) is suspended meanwhile. Ram's bulletin 08-171-26 for 2025-26 Ram 2500 to 5500 trucks links U0615 on the coolant three-way valve to a contaminated connector under the coolant bottle; the fix is dielectric grease, or a new valve plus pigtail. Drivers notice the lamp and weak cabin heat. Circuit faults of the valve are P2681 to P2683.
- What you may notice
- Check engine light
- Little or no cabin heat
- Engine warms up slower or coolant temperature behaves unusually
- Likely causes
- LikelyMoisture or corrosion in the valve connector (Ram bulletin 08-171-26)
- PossibleLIN, supply or ground wire to the valve open, shorted or chafed
- PossibleValve actuator electronics failed (valve no longer answers)
- RareLIN master in 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.