P2ACEReductant Temperature Sensor B Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2ACE means the signal of reductant temperature sensor B lies below its valid voltage band. With the NTC elements used for DEF temperature, a low voltage translates into an extremely hot reading, so a signal line rubbing through to ground, a crushed connector or DEF that has wicked into the plug and bridges the contacts are the usual suspects. No maker publishes a threshold for P2ACE. For sensor A, Deutz lists P2044-00 as a short to ground; GM's 2025 DEF controller sets the low limit of its tank sensor at 0.3 V, roughly 75 °C, which shows the order of magnitude. A false hot value can lead the controller to skip DEF heating in frost, so lines may freeze and dosing stop. Measure the sensor resistance against a temperature table and look for crystallised DEF at the connector.
- What you may notice
- Check engine light and SCR warning
- Implausibly high DEF temperature in live data
- Frozen DEF lines in winter
- Likely causes
- LikelySignal wire of sensor B shorted to ground
- PossibleDEF wicked into the connector bridging the terminals
- PossibleSensor B internally shorted
- 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.