Powertrain, generic (extended)

P2D5A Reductant Level Sensor A/B Correlation

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2D5A compares two level sensors of the diesel exhaust fluid system: each delivers a valid signal, yet together they describe a fill level that cannot be true. Tanks with several level contacts, or vehicles with a main and an auxiliary tank, can cross-check their sensors this way. No manufacturer documents P2D5A on an official public source. GM's 2014 diesel tables show the idea under P203B: the module pulses three discrete level contacts and reports a fault after 5 s, Type B, when the readings form an impossible combination, for instance sensor 2 in its 0 to 1.7 V band while sensor 1 sits at 1.71 to 3.56 V. California requires the level sensor to be monitored as input to driver inducement. A wrong reading can bring early warnings or the inducement countdown.

Likely causes

One level sensor failed or contaminated
Urea crystals or deposits on the sensing elements
Corrosion or poor contact at the tank sensor connector

Symptoms

  • Implausible or jumping DEF level display
  • MIL and DEF warning message
  • Possible inducement countdown despite sufficient fluid

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–1,200
Time0.5–3 h

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

Parts involved

reductant level sensorreductant tankscr module

Related codes

P203BP21A9P21C5P21C6P203AP21A8

References: gsi.ext.gm.com, law.cornell.edu.