Powertrain, generic (extended)

P2ACF Reductant Temperature Sensor B Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Open signal wire or disconnected plug at sensor B
Missing sensor ground
Signal wire shorted to supply voltage

Symptoms

  • Check engine light and SCR warning
  • Implausibly low DEF temperature in live data
  • Delayed start of dosing after a cold start

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–900
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant temperature sensor bwiring harness

Related codes

P2ACCP2ACEP2ACDP2AD0P2045

References: serdia.deutz.com, gsi.ext.gm.com, law.cornell.edu.