P2001 NOx Adsorber Efficiency Below Threshold (Bank 2)

P2001 belongs to the second cylinder bank: the NOx storage catalyst fed by bank 2 has lost so much capacity that it no longer holds and reduces the nitrogen oxides of lean running. The code is only possible on V or boxer engines that give each bank its own trap. No manufacturer documents P2001 publicly; the best documented trap application, the inline-six 6.7 L Cummins in Ram pickups, has a single bank and reports P2000. CARB sets the same emission-based limit for every NOx adsorber, so the bank 2 monitor works like its bank 1 sibling, comparing what the sensors behind the trap see during storage and purge with a model. Usual suspects are sulphur that desulphation can no longer burn off, a heat-damaged coating, misreading sensors on that side or purges cut short. The car keeps driving normally.

Likely causes

Symptoms

• Malfunction indicator lamp on
• Driveability usually unchanged

Repair estimate

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

Parts involved

Related codes

References: law.cornell.edu, static.nhtsa.gov, en.wikipedia.org.