HC Adsorption Catalyst Efficiency Below Threshold - Bank 1
What does P2423 mean?
The P2423 code means the vehicle's onboard diagnostic system has detected: HC Adsorption Catalyst Efficiency Below Threshold - Bank 1. This is a moderate severity code.
Common Symptoms
- Check Engine Light illuminated
- Failed emissions test for hydrocarbons
- Slight fuel odor from exhaust
- No major drivability symptoms
- Reduced catalytic converter efficiency readings
Probable Causes (Ranked by Likelihood)
- Degraded or contaminated HC adsorption catalyst Very High
- Engine running too rich contaminating the catalyst High
- Exhaust leak before the catalyst Moderate
- Incorrect fuel type or contaminated fuel Low
Step-by-Step Diagnostic Procedure
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Check for additional fuel trim or O2 sensor codes indicating rich running
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Inspect the exhaust system for leaks before the catalyst
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Evaluate catalyst efficiency using upstream and downstream O2 sensor data
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Check fuel trims to ensure the engine is not running excessively rich
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Inspect for oil burning that could contaminate the catalyst
Frequently Asked Questions
Can I drive with code P2423?
Short distances are acceptable. The vehicle will have higher hydrocarbon emissions and will fail emissions testing until repaired.
What causes P2423?
Usually a degraded HC adsorption catalyst, commonly seen on European vehicles with close-coupled catalysts. Rich running conditions accelerate catalyst degradation.
Is P2423 expensive to fix?
Costs range from $200 to $1500. Catalyst replacement on European vehicles is the most expensive repair. Address any rich-running condition first to prevent recurrence.