Powertrain, generic (extended)

P20E2 Exhaust Gas Temperature Sensor 1/2 Correlation (Bank 1)

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P20E2 flags that bank 1 exhaust temperature sensors 1 and 2 disagree at a moment when both should show nearly the same value. Sensor 1 usually sits ahead of the oxidation catalyst and sensor 2 behind it. GM runs this check on the 6.6 L Duramax LML/LGH (table 15OBDG09) and on the diesel of table 15OBDG04: after at least 28,800 s (8 h) with the engine off, the two readings captured at start-up are compared, and a gap above a limit taken from a look-up table counts as a Type B fault, so the MIL lights after two failing trips. A sensor that is offset but still inside its valid voltage window passes the circuit checks P0544 and P2031–P2033 and is only caught here. Drivers rarely notice more than the lamp, although GM blocks some regeneration functions while this code is active.

Likely causes

Exhaust temperature sensor 1 or 2 drifted or aged (offset reading)

Corroded or loose connector adding resistance to one sensor signal

Sensors swapped or a non-matching replacement part installed

Engine control software needing an update

Symptoms

Malfunction indicator lamp on, often with no change in driving
Particulate filter regeneration delayed or blocked
Code returns after a long parking period

Repair estimate

DifficultyMediumDIY possible

Parts and labour€60–400

Time0.5–2.5 h

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

Parts involved

exhaust gas temperature sensorwiring harness

References: gsi.ext.gm.com, gsi.ext.gm.com, patents.google.com.