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U016D Lost Communication With Exhaust Gas Sensor Module B

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

U016D refers to exhaust gas sensor module B, a second smart sensor unit in the exhaust that heats a probe, evaluates it and reports oxygen or NOx readings as bus data instead of an analog voltage. Module A has U011A. Which sensor counts as B depends on the maker, for instance the other bank or a probe further downstream behind an SCR catalyst. No manufacturer documents U016D publicly, and the NHTSA bulletin index has no entry for it. CARB 13 CCR 1968.2 obliges OBD to flag a lost digital link from such an input with its own code, and exhaust and NOx sensors are emission monitors in their own right, so the MIL is normally lit. Mixture correction, catalyst checks or urea dosing may fall back to defaults. U046E is invalid data from module B.

Likely causes

Sensor module connector or harness damaged by exhaust heat or corrosion
Sensor module without power or ground (fuse, relay)
Bus line to the module chafed under the vehicle
Sensor module B or integrated probe electronics faulty

Symptoms

  • Check engine light on
  • Readiness monitors for catalyst or exhaust sensors not complete
  • Diesel: SCR or emission warning, possibly reduced power

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–900
Time0.5–3 h

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

Parts involved

exhaust gas sensor module bcan bus wiring

Related codes

U011AU046E

References: law.cornell.edu, hella.com, en.wikipedia.org.