P20ADReductant Metering Unit Temperature Sensor Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P20AD covers a metering unit temperature reading that is electrically valid but does not make sense. A typical check compares it after a long cold soak with other temperatures that ought to agree, or watches whether it climbs once the module heater or warm coolant has had time to act. Hino gives a practical yardstick in tech tip TT-16-014: with the engine at ambient temperature, DEF tank, DEF pump and coolant readings should lie within 8 °C (14 °F) of each other; Hino applies that to its coolant valve code P20B2, not to P20AD. No manufacturer publishes P20AD with its own limits. Because the verdict rests on behaviour over time, confirmation usually needs a complete drive cycle, and a skewed value can mislead the thaw and heating logic.
- What you may notice
- Warning lamp after a cold start or longer drive
- DEF dosing starts late or not at all in winter
- Live data shows module temperature out of line with tank and coolant
- Likely causes
- LikelyTemperature sensor in the metering unit drifted (reads plausible but wrong)
- PossibleComparison sensor (DEF tank or coolant temperature) itself faulty
- PossibleContact resistance in the connector shifting the signal
- RareModule heating or coolant heating not working, so the expected rise never comes
- 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 – €1,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.