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U0653 Lost Communication With EGR Sensor C

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

On GM's 2025 diesel with high- and low-pressure EGR (table 25OBDG04B), EGR sensor C is the SENT position sensor of the low-pressure valve, which as usual for such loops takes exhaust after the particulate filter and feeds it ahead of the compressor. Oddly, the table's text calls this valve the B position sensor while filing its codes under C. U0653 is stored when 480 of 600 checks every 6.25 ms see outdated data while the protocol sits permanently low or high, a corrupt message, or counters that froze; GM rates this Type A, lighting the MIL on the first trip. A raw level below 1 % on the same sensor is P044C, and P044A to P044E cover the analog faults of sensor C. While the low-pressure valve position is unknown, its loop is shut and the high-pressure loop has to cover alone.

Likely causes

Wiring to the low-pressure EGR valve damaged near the exhaust

Connector corroded by road splash

Position sensor in the low-pressure EGR valve failed

Engine controller input fault

Symptoms

MIL on from the first trip
Low-pressure EGR disabled, higher NOx
EGR monitor not ready

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€60–900

Time0.5–3.5 h

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

Parts involved

egr sensor cvehicle bus wiring

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