P2ADDReductant Tank Temperature Sensor B Circuit Intermittent/Erratic
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2ADD judges how the sensor B signal moves over time instead of how high it is. Fluid in a tank warms and cools slowly, so sudden jumps suggest a loose contact or a failing element. GM's 2017 and 2018 diesel tables compare every raw thermistor sample with an envelope that starts at the last good value and widens toward the −55 °C and 155 °C limits as bad samples pile up; 40 failures in 50 samples give a Type A code. In the 2025 DEF controller the tank unit adds up the absolute temperature changes across a window of 14 samples taken every 1.3 s and fails above 6 °C, one fail in three windows being enough; while P2ADB or P2ADC is present this test is suspended. GM also lists P2ADD in bulletin 21-NA-149 on harness chafing with the 3.0 L LM2 diesel.
- What you may notice
- Check engine light that may return after clearing
- Jumping DEF temperature in live data
- DEF or SCR warning message
- Likely causes
- LikelyLoose or corroded contact at the tank sensor connector
- PossibleChafed harness with intermittent contact
- PossibleDegrading thermistor in the quality or tank sensor 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: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.