System: Powertrain (P-Code)
SAE Standard (Generic)
Family: NOx Adsorber Efficiency
Code P2001: NOx Adsorber Efficiency Below Threshold Bank 2
Diagnostic & Technical Explanation
Code P2001 (NOx Adsorber Efficiency Below Threshold Bank 2) indicates the NOx adsorber is no longer storing and converting oxides of nitrogen at the rate the aftertreatment model expects during its periodic efficiency check. Adsorber substrate that has thermally aged or become sulfur- and lubricant-poisoned loses storage capacity first, followed by a rich-regeneration event that never fully purges the trap, and occasionally by a NOx sensor drifting enough to make a healthy trap read as inefficient.
First-listed procedure
Rank #1
Perform a forced NOx adsorber regeneration with a scan tool
Moderate DIY
This is the first procedure in the authored
consideration order, not a measured cause likelihood. Execute it only when its prerequisites
and diagnostic findings support it. Its cost and labor estimates (where known), the step-by-step procedure and the
remaining 3 procedure(s) are in the licensed dataset. Ordering context.
Full family: NOx Adsorber Efficiency
What this page does not show
This page publishes the fault mechanism and the code index. The licensed dataset adds, for
every one of the 15,886 codes, the full authored repair set (56,729 procedures in total)
with the fields deliberately withheld here:
- Procedures 2..n after the first-listed procedure
- Aftermarket parts cost ranges in USD (
est_parts_cost_min/max_usd)
- Professional labor-hour estimates (
est_labor_hours)
- Step-by-step diagnostic and repair instructions
- Replacement-part mappings and catalog lookups
- 6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)