Powertrain, generic (extended)

P2ADC Reductant Tank Temperature Sensor B Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Internal fault in the quality sensor or smart tank sensor unit
Chafed engine harness disturbing the sensor circuit
Corroded or loose pins at the tank sensor connector

Symptoms

  • Check engine light on
  • DEF system message, often together with other harness-related codes
  • Possible inducement countdown toward reduced power

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€150–1,500
Time0.5–4 h

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

Parts involved

reductant tank temperature sensor bwiring harnessscr module

Related codes

P2ADAP2ADBP2ADDP2ADEP205D

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.