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U05A2 NOx Sensor B Received Invalid Data From ECM/PCM

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

This is the downstream counterpart of U05A1: the tailpipe NOx sensor B finds the frames it gets from the engine controller missing or implausible and reports it. Ford's 2023 diesel summary documents it for the 3.0 L and 6.7 L engines next to P229E in the tailpipe NOx controller checks, using the same criteria as for the front sensor, an erroneous signal such as a dew point release with ignition off, or more than 1 s without a message, confirmed after 5 s. Ford's 2014 list also shows it with MIL. Because sensor B measures what leaves the SCR catalyst, the efficiency monitor cannot finish while the code is active. U059F describes the reverse problem, U029E a sensor that has gone quiet. A software update or bus repair usually comes before replacing the sensor.

Likely causes

Damaged harness to the rear sensor, exposed to road spray and heat
Engine controller software sending implausible commands
Fault inside the sensor B control unit

Symptoms

  • Check engine light on
  • SCR efficiency monitor incomplete

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–900
Time0.5–2 h

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

Parts involved

nox sensor becm

Related codes

U059FU05A1U05A9U029EP229E

References: fordservicecontent.com, performanceparts.ford.com, law.cornell.edu.