P28F4Engine Disconnect Clutch Pressure Sensor Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- With P28F4 the disconnect clutch pressure sensor sends a voltage above anything it could produce even at full clutch pressure. Typical reasons are a signal line touching the reference or battery supply, an open sensor ground, or on inputs with a pull-up resistor a signal wire that is broken at the sensor. No manufacturer publishes a threshold for P28F4. The sensor matters because the controller closes the clutch by pressure: Ford mounts one on the clutch of its 10R80 hybrid gearbox, while Hyundai notes in a patent that a reading wrongly offset from the real pressure makes the clutch slip. A falsely high value would suggest a firmly closed clutch. CARB obliges the maker to test such inputs against their valid range. P28F3 is the low fault. Most systems stop using the clutch until the fault clears.
- What you may notice
- Hybrid or transmission warning light
- Clutch slips when the engine is meant to drive
- Electric-only operation or reduced power
- Likely causes
- LikelySignal wire shorted to sensor reference or battery voltage
- PossibleSensor ground open or corroded at the connector
- PossiblePressure sensor failed with output stuck high
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.