P20ACReductant Metering Unit Temperature Sensor Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P20AC is the general circuit code for the temperature sensor built into the reductant metering unit, meaning the DEF supply or dosing module that pressurises the fluid. The control unit typically relies on this value to judge whether the module has thawed and may start pumping. The code stands for an electrical fault the software cannot assign to a low or high signal; those cases carry their own numbers, P20AE and P20AF. No manufacturer documents P20AC publicly. Hino, for example, files faults of its DEF pump temperature sensor under the maker-specific P142A instead. CARB requires such inputs to be watched continuously for circuit continuity. Drivers see a DEF or engine warning and, if it is ignored, speed or restart limits.
- What you may notice
- Malfunction indicator or DEF/SCR warning lamp on
- Dosing delayed or stopped in cold weather
- Inducement countdown with speed or restart limit
- Likely causes
- LikelyCorroded or loose connector at the DEF supply/metering module
- PossibleDamaged sensor wiring between module and control unit
- PossibleTemperature sensor inside the metering unit failed (usually replaced with the module)
- RareInput fault in the dosing or engine control unit
- 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 – €1,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.