System: Powertrain (P-Code)
SAE Standard (Generic)
Family: HC Adsorption Catalyst Efficiency
Code P2423: HC Adsorption Catalyst Efficiency Below Threshold Bank 1
Diagnostic & Technical Explanation
Code P2423 (HC Adsorption Catalyst Efficiency Below Threshold Bank 1) sets when the ECM's cold-start hydrocarbon trap monitor finds the adsorption catalyst is no longer capturing and later burning off unburned hydrocarbons during the first seconds after a cold start as effectively as its calibrated threshold requires. Causes are thermal aging of the adsorption bed's washcoat from repeated heat exposure, physical substrate damage, or an exhaust leak upstream of the trap diluting the sample the ECM uses to judge efficiency.
First-listed procedure
Rank #1
Repair upstream exhaust leak
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 2 procedure(s) are in the licensed dataset. Ordering context.
Full family: HC Adsorption Catalyst 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)