Failure mode - GM 3.0L Duramax LM2/LZ0 I6 (2020+)

NOx sensor / SCR efficiency codes

Reliability tier: aggregated - verify before ordering, see /disclosure/

Symptoms

P20EE (NOx catalyst efficiency) and NOx sensor circuit codes, CEL
may accompany the DEF derate ladder when SCR efficiency reads low

Compare with the other causes of the same sign on this engine: loss of power, limp mode or derate (7 causes) · def, dpf and regeneration warnings (4 causes)

Root cause

NOx sensor failures / efficiency codes - the standard SCR-era sensor replacement item. 4 VIN-confirmed NHTSA complaints (thin), consistent with the GM diesel pattern (sensors are a documented L5P/LML item too).

Diagnosis

confirm which sensor position is coded before ordering (GM splits position 1/2)

Fixes

replace the coded NOx sensor (position split per GM) ()

nox-sensor - more than one option: 3.0L Duramax NOx Sensor, Position 1 (GM 24001898), 3.0L Duramax NOx Sensor, Position 2 (GM 24001899), 3.0L Duramax NOx Sensor, Position 3 (GM 24001900)

Prevalence

occasional