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U069A Lost Communication With Exhaust Gas Temperature Sensor Bank 1 Sensor 3

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

The third exhaust temperature sensor on bank 1 usually sits in the aftertreatment, ahead of the filter or SCR stage. GM covers U069A in both 2025 diesel tables, 25OBDG04A and 25OBDG04B: a SENT sensor whose output was switched off by an internal fault, or that sends faulty or outdated messages, fails the check once 19 readings out of 25, taken every 100 ms, are bad. The test waits for the sensor start-up delay and skips cranking; Type A, so the lamp lights in the first faulty trip. GM's regeneration control reads EGT 3 as the temperature ahead of the particulate filter, and the circuit-low test P242C treats a digital reading under -72.8 °C as faulty. Ford's 2023 diesels have sensor 3 as an analog probe (P242C/P242D, below 0.10 V or above 2.66 V). Sensor 4 is U069B.

Likely causes

Sensor harness along the aftertreatment burnt or chafed

Electronics module of the thermocouple sensor failed

Connector corroded

Controller input fault

Symptoms

Check engine light, on GM diesels in the first trip
Particulate filter regeneration blocked or postponed
Further code for the controller input

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 3vehicle bus wiring

References: gsi.ext.gm.com, gsi.ext.gm.com, fordservicecontent.com.