P2ACFReductant Temperature Sensor B 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
- P2ACF is set when reductant temperature sensor B reports a voltage above its valid band. For a thermistor that reads as deep cold, and it is what an open signal wire, a missing sensor ground, a disconnected plug or a short to supply voltage cause. No public document gives a limit for P2ACF; Deutz records the A-side equivalent as P2045-00, short to battery, and keeps the plain open circuit apart as P2042-13. For orientation, GM's 2025 DEF controller treats more than 4.75 V on its tank sensor, about −40 °C, as the high fault. A sensor that falsely reports frost can keep heaters running longer than needed and delay the start of dosing after a cold start, which raises NOx until it clears. Test the ground path and the sensor resistance at a known temperature.
- What you may notice
- Check engine light and SCR warning
- Implausibly low DEF temperature in live data
- Delayed start of dosing after a cold start
- Likely causes
- LikelyOpen signal wire or disconnected plug at sensor B
- PossibleMissing sensor ground
- RareSignal wire shorted to 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: €80 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.