P2CA4Particulate Filter Pressure Sensor Signals Swapped A/B
- 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
- P2CA4 means the engine module believes the readings of particulate filter pressure sensors A and B arrive on each other's inputs, typically because connectors, sensors or sensing hoses were interchanged during service. Such a mix-up yields values that look electrically sound but invert the pressure picture across the filter. No manufacturer documents P2CA4 publicly. Comparable checks exist: Ford's 2015 diesel summary cross-checks its absolute and delta filter pressure sensors under P246D and sets it above 1.5 kPa disagreement, and Ford's 2020–23 petrol summary flags reversed EGR delta-pressure hoses (P139A) once its signal sits under −0.5 kPa for half a minute. CARB requires plausibility checks on PM filter sensors. Wrong soot loading and mistimed regeneration follow.
- What you may notice
- MIL on, usually right after work on the exhaust or sensors
- Regeneration too frequent or not taking place
- Implausible filter pressure values in live data
- Likely causes
- LikelySensing hoses of sensors A and B fitted to the wrong ports
- LikelyElectrical connectors of the two sensors interchanged after service
- PossibleReplacement sensor with different pin assignment or range
- RareCrossed wires after a harness repair
- 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: €0 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.