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U0620 Lost Communication With Exhaust Gas Temperature Sensor Bank 1 Sensor 2

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

Sensor 2 on bank 1 is the next exhaust temperature measuring point downstream of sensor 1; on diesels it usually sits ahead of the particulate filter or the SCR catalyst, depending on how the maker numbers its sensors. U0620 is the lost-communication code for this point when it is a digital sensor: its frames have stopped, are too old, or its own diagnosis has switched the SENT output off. GM uses it in the same 2025 diesel tables as U061F with an identical rule (19 bad out of 25 samples at 100 ms, Type A), and again a second code identifies the controller input the sensor is connected to. Monitors and regeneration decisions that need this temperature cannot use it while the link is down. An analog sensor at the same position reports circuit faults as P2031 to P2033.

Likely causes

Signal, supply or ground wire of the sensor damaged near the exhaust

Moisture or corrosion in the underbody connector

Sensor electronics module failed

Symptoms

Malfunction indicator lamp in the first trip on GM diesels
Diesel particulate filter or SCR warnings may follow

Repair estimate

DifficultyMediumDIY possible

Parts and labour€60–450

Time0.5–2 h

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

Parts involved

egt sensor bank 1 sensor 2sensor wiring

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