Network, generic

U010B Lost Communication With Exhaust Gas Recirculation Control Module B

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U010B names the second exhaust gas recirculation control module, B. Its existence implies an engine with two separately controlled EGR units, for example a high- and a low-pressure loop on a diesel or one unit per cylinder bank; which one is B is the maker's choice. The code itself only says that a node expecting periodic messages from module B no longer receives them. Neither a manufacturer document nor any entry in the NHTSA bulletin index names U010B. Diagnosis therefore follows the generic path: supply, ground and bus lines of module B first, then the module. If only B is silent while A (U010A) still talks, the fault sits in B's branch. Invalid data from B is U040C; CARB's EGR monitoring makes the code emission-relevant.

Likely causes

EGR module B without power or ground
Open or chafed bus branch to module B
Loose or heat-damaged connector at module B
EGR module B internally faulty

Symptoms

  • MIL on
  • Second EGR path inactive, possible NOx increase
  • Module B not reachable with a scan tool

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–900
Time0.5–3 h

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

Parts involved

egr module bcan bus wiring

Related codes

U010AU040CU010D

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