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

What does P20E2 mean?

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.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

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

Common causes

• High Exhaust temperature sensor 1 or 2 drifted or aged (offset reading)
• Medium Corroded or loose connector adding resistance to one sensor signal
• Low Sensors swapped or a non-matching replacement part installed
• Low Engine control software needing an update

Likelihood is a general estimate across vehicles; your make and model may differ.