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U02A2 Lost Communication With Reductant Quality Module

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

The reductant quality module tells the engine or dosing controller whether the tank holds proper diesel exhaust fluid; in many trucks it is one tank sensor unit with level and temperature. U02A2 means its messages have stopped. Ford's 2023 diesel summary allows 5 s without them. In TSB 19-2315 Ford blames water in connectors C3613 and C4851 of the reductant harness on the 6.7 L F-Super Duty of model years 2017-2019 and replaces harness, pump and heater assembly or tank. Hino's SB-15-030 for 2014 and 2015 trucks points to a faulty DEF tank sensor assembly and supplies a more robust one. Mack lists software faults, missing supply and the connector. CARB 1968.2 requires every input of the inducement strategy to be monitored, so the warning sequence that leads to a speed limit may begin.

Likely causes

Water in the reductant harness connectors at tank or pump
Defective DEF tank sensor unit with quality sensor
Missing supply voltage or wrong software version of the module
Damaged CAN wiring between tank sensor and controller

Symptoms

  • MIL and DEF system warning
  • Countdown to speed or restart limitation
  • DEF quality and level readings missing

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,800
Time0.5–4 h

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

Parts involved

reductant quality modulevehicle bus wiring

Related codes

U05A3U030CP203BP206BP21CDP21DD

References: fordservicecontent.com, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.