Powertrain, generic (extended)

P2423 HC Adsorption Catalyst Efficiency Below Threshold (Bank 1)

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

Some very low emission petrol engines add a hydrocarbon trap: an adsorbing layer holds back unburned fuel during a cold start and releases it once the main catalyst has lit off. P2423 means the bank 1 trap no longer retains enough. Nissan uses the code, named HC adsorption catalyst function, on the 2010-2012 Altima with the QR25DE in California SULEV form. Its bulletin NTB20-020 stretches warranty on the front exhaust pipe that carries the catalyst to 16 years/170,000 miles for 2010-2011 cars and 10 years/120,000 miles for 2012, tied to an ECM reprogramming campaign. Nissan does not publish the threshold. CARB places such traps under other emission controls with an approved monitoring plan. The car drives normally.

Likely causes

Adsorber layer aged or saturated with deposits

ECM calibration affected by a manufacturer campaign (Nissan Altima SULEV)

Damage from misfires or oil consumption

Symptoms

Check engine light, no noticeable driving change
Higher cold-start hydrocarbon emissions

Repair estimate

DifficultyHardWorkshop job

Parts and labour€100–2,500

Time0.5–3 h

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

Parts involved

hc adsorber catalyst

Related codes

P2424 P0420

References: static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.