P05C4Engine Coolant Pressure Sensor Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Needs a drive cycle to confirm a fix
- How the car detects it
- An engine coolant pressure sensor (5 V reference, ratiometric signal) measures pressure in the cooling circuit; in a sealed circuit pressure rises with temperature, so deviations reveal leaks or a loose cap – described in Navistar and GE patents for commercial and rail engines. No manufacturer document available to us uses P05C2–P05C6 for passenger cars; CARB requires input components to be checked for circuit faults, range and plausibility. P05C4 means the signal voltage is below its limit – usually a signal shorted to ground, an open signal line or a missing 5 V reference, not low coolant pressure.
- What you may notice
- Check engine light or warning (depending on the maker)
- Coolant pressure or leak warning unavailable
- Usually no change in driving
- Likely causes
- LikelySignal line shorted to ground or open
- Possible5 V reference open or shorted
- PossibleSensor faulty
- PossibleConnector corroded
- Repair
- Easy · Often possible to do yourself.Typical cost: €50 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.