P0E84Auxiliary Cooling System Coolant Temperature Sensor A Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P0E84 is the high-voltage case for sensor A of the auxiliary loop: the signal sits near the reference voltage, which an NTC thermistor would only produce at extreme cold. Far more often the circuit is open, from an unplugged connector, a broken wire or a sensor with an internal break, or the signal line is shorted to a voltage source. The module then cannot judge the temperature of that loop and falls back to substitute values, which can make heater or pump control less precise. No manufacturer documents P0E84 publicly. Ford's 2019 hybrid summary uses P2185 for the equivalent fault of its heater-loop sensor ECT2, set after the driver signals a fault for 5 seconds. CARB wants temperature inputs tested for readings beyond their valid span. P0E83 is the low counterpart.
- What you may notice
- Check engine light
- Scan tool shows the loop at minimum temperature
- Less precise cabin heating
- Likely causes
- LikelyUnplugged connector or broken sensor wire
- PossibleSensor A open internally
- RareSignal wire shorted to a voltage source
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €40 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.