P20AFReductant Metering Unit Temperature 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
- P20AF means the metering unit temperature signal has risen above its permitted band. For an NTC thermistor, the likely design though not publicly confirmed for this part, that looks like an extremely cold module. Electrically it is usually an open signal or ground wire, a terminal backed out of the connector or a short to a voltage source. Corrosion deserves attention: Hino's bulletins SB-16-015 and SB-16-016 explain that frozen DEF can damage the pump and let fluid creep into the pump connector and SCR harness; Hino names its own P142A there, not P20AF. Believing the module frozen, the control unit holds back dosing and may keep heating. No maker publishes P20AF itself.
- What you may notice
- Module temperature shown far below ambient in live data
- DEF warning and delayed or missing dosing
- Further SCR codes if the harness is corroded
- Likely causes
- LikelyOpen signal or ground wire to the temperature sensor
- PossibleDEF intrusion and corrosion in the pump connector or harness
- PossibleSensor element in the metering unit open
- RareSignal wire shorted to a supply voltage
- 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: €60 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.