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U068F Lost Communication With EGR Temperature Sensor C

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

Engines with both a high- and a low-pressure EGR loop need more temperature points, which is where slots C and D come in. U068F means the controller lost the digital messages of EGR temperature sensor C. There is no public manufacturer documentation for it. In GM's 2025 diesel table 25OBDG04B, sensor C is an air temperature point upstream in the low-pressure EGR path, read as a resistance: below 7 ohms it gives P04D0 after 30 of 38 counts, Type A, and after more than 8 hours off it may not stray over 20 °C from the mean of intake air and fuel temperature at key-on (P04CF). A SENT version with its own lost-communication check is not listed there. CARB requires separate detection when a digital input is silent. Analog faults are P04CE to P04D2. Low-pressure EGR is then usually reduced or switched off.

Likely causes

Wiring to sensor C near the exhaust aftertreatment damaged

Connector corroded by road splash

Sensor electronics failed

Symptoms

Check engine light
Low-pressure EGR reduced or disabled

Repair estimate

DifficultyMediumDIY possible

Parts and labour€60–400

Time0.5–2 h

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

Parts involved

egr temp sensor cvehicle bus wiring

References: gsi.ext.gm.com, law.cornell.edu.