Powertrain, generic (extended)

P2ADD Reductant Tank Temperature Sensor B Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Loose or corroded contact at the tank sensor connector
Chafed harness with intermittent contact
Degrading thermistor in the quality or tank sensor unit

Symptoms

  • Check engine light that may return after clearing
  • Jumping DEF temperature in live data
  • DEF or SCR warning message

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–1,500
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

P2ADAP2ADBP2ADCP2ADEP205E

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