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U059E Invalid Data Received From NOx Sensor A

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

NOx sensor A usually sits upstream of the SCR catalyst. Its attached electronics turn the probe current into NOx and oxygen readings and broadcast them on CAN. Here those frames still arrive, yet the receiver rejects them. GM's 2025 diesel ECM tables (25OBDG04A/B) count wrong alive rolling counts, protection values or checksums: 8 bad out of 18 samples for most signals, 3 out of 10 for a few, with at least 11 V present for 5 s. It is Type B, so the MIL follows on the second trip. Ford's 2023 diesel summary sets it when the sensor's calibration verification number never reaches the ECU. U029D stands for a silent sensor, U05A1 for the reverse path. Until valid readings return, NOx-based SCR checks and dosing feedback cannot run.

Likely causes

Sensor control unit of NOx sensor A faulty (heat, moisture, internal error)
Replacement sensor of a different part number or software level
Corroded connector or damaged CAN/supply wiring at the sensor
Engine controller software needing an update

Symptoms

  • Check engine light after the second faulty trip
  • SCR and NOx sensor monitors stay incomplete
  • Engine usually runs normally

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€150–900
Time0.5–2 h

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

Parts involved

nox sensor a

Related codes

U029DU059FU05A8U05A1U030DP2200

References: gsi.ext.gm.com, fordservicecontent.com, bosch-mobility.com, law.cornell.edu.