P0E78Coolant Bypass Valve A Control Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P0E78 is the plausibility code for the actuator circuit of bypass valve A. Neither an open nor a short is present, yet current, feedback or response time of the actuator do not fit what the module has commanded: a coil whose resistance has drifted, a motor that labours against a sticky shaft, or a supply that sags under load. For motor-driven valves with position feedback the module may also see the valve arrive late or stop short. No manufacturer documents P0E78 publicly. Ford's hybrid summary for 2019 shows the general idea of checking the actual valve position once an electrical problem is known, under P26AB. CARB asks for functional checks of output components in addition to circuit tests. Hard electrical faults are P0E75 to P0E77; a valve that stays put is P0E79 or P0E7A.
- What you may notice
- Check engine light
- Heating output varies from trip to trip
- Likely causes
- LikelyDeposits or wear making the valve A mechanism sluggish
- PossibleHigh resistance at connector or ground of the valve circuit
- RareLow supply voltage to the actuator under load
- 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: €80 – €550
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.