What Does P2423 Mean?
The PCM has determined that the hydrocarbon adsorption catalyst on Bank 1 is not efficiently trapping hydrocarbons during cold starts. Efficiency has fallen below the minimum threshold.
Common Causes
50%
Degraded or saturated HC adsorption catalyst material
20%
Engine oil or coolant contamination poisoning catalyst material
15%
Exhaust leaks before HC catalyst reducing effectiveness
10%
Faulty temperature sensor providing incorrect catalyst temp data
5%
Rich fuel mixture overwhelming catalyst capacity
Diagnostic Steps
1
Step 1: Inspect exhaust system for leaks upstream of Bank 1 HC catalyst
2
Step 2: Check for oil consumption or coolant loss that may indicate catalyst contamination
3
Step 3: Monitor catalyst temperature sensors during cold start to verify proper reading and heating
4
Step 4: Check fuel trims and O2 sensor data for rich running conditions that may overload catalyst
5
Step 5: Perform catalyst efficiency test comparing upstream vs downstream HC sensor readings if equipped
Estimated Repair Cost
$400 - $1,500
Parts + labor, varies by vehicle and location
The PCM has determined that the hydrocarbon adsorption catalyst on Bank 1 is not efficiently trapping hydrocarbons during cold starts. Efficiency has fallen below the minimum threshold.
The most common cause of P2423 (HC Adsorption Catalyst Efficiency Below Threshold Bank 1) is: Degraded or saturated HC adsorption catalyst material
Typical repair costs for P2423 range from $400 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. Increased cold-start emissions only. Will fail emissions testing in some jurisdictions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2423 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control System
Difficulty
Type
Generic (SAE)
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