P2ADCReductant Tank 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
- P2ADC is the upper limit check on the same sensor B: the reported DEF temperature is higher than the fluid in the tank could ever get. In GM's 2017 and 2018 diesel calibrations the quality sensor thermistor has to exceed 155 °C in 40 of 50 samples, with cranking finished and more than 11 V at the powertrain relay; the outcome is a Type A code. GM's 2025 DEF controller draws the line much lower at 90 °C, held for 2 s and again computed inside the smart tank unit. GM bulletin 21-NA-149 names P2ADC among the codes that a chafed engine harness produced on 2021 trucks and SUVs with the 3.0 L LM2 diesel. Such a high value usually means trouble in the sensor electronics or its wiring rather than real heat. Too low and unsteady signals are handled by P2ADB and P2ADD.
- What you may notice
- Check engine light on
- DEF system message, often together with other harness-related codes
- Possible inducement countdown toward reduced power
- Likely causes
- LikelyInternal fault in the quality sensor or smart tank sensor unit
- PossibleChafed engine harness disturbing the sensor circuit
- RareCorroded or loose pins at the tank sensor connector
- 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: €150 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.