Network, generic

U0652 Lost Communication With EGR Sensor B

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

U0652 covers a digital EGR sensor labelled B that has stopped delivering data. What B measures depends on the maker; it may be the position of a second valve or a pressure or temperature signal of the EGR path. No manufacturer documents U0652 publicly. GM's 2025 diesel table 25OBDG04B shows how loose the lettering is: it uses U0651 for the high-pressure valve and U0653 for the low-pressure valve, whose text even calls it the B position sensor, yet U0652 does not appear at all. Sections (e)(15.2.1)(B)(i) and (f)(15.2.1)(B)(i) of the CARB rule require a separate code when a digital input stops communicating. An analog sensor B reports P0486, P0407, P0408 and P046E. Whatever B serves, its EGR function and monitor are suspended until data returns.

Likely causes

Wiring to EGR sensor B open, shorted or heat-damaged

Connector at sensor B corroded or loose

Sensor B electronics failed

Engine controller input fault

Symptoms

MIL on
EGR monitor incomplete
Possibly reduced EGR operation

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

egr sensor bvehicle bus wiring

References: law.cornell.edu, en.wikipedia.org, gsi.ext.gm.com.