P2423 - HC Adsorption Catalyst Efficiency Below Threshold Bank 1
The P2423 code indicates that the hydrocarbon (HC) adsorption catalyst efficiency is below the expected threshold for Bank 1. This catalyst is part of the evaporative emission control system, designed to trap fuel vapors during cold starts. When efficiency drops, it may fail to capture hydrocarbons, leading to increased emissions. Common causes include a degraded or contaminated catalyst, exhaust leaks, or issues with the oxygen sensors that monitor catalyst performance.
01. Most Common Causes
- Faulty HC adsorption catalyst
- Exhaust system leaks before the catalyst
- Oxygen sensor malfunction (upstream or downstream)
- Engine misfire causing excess hydrocarbons
- Contaminated catalyst due to oil or coolant leakage
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Possible rough idle or hesitation
- Decreased fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan the vehicle for codes and record freeze frame data.
Step 2: Inspect the exhaust system for leaks, especially before the catalyst.
Step 3: Check oxygen sensor readings using a scan tool to ensure proper switching.
Step 4: Perform a catalyst efficiency test by monitoring oxygen sensor voltage and comparing pre- and post-catalyst signals.
Step 5: If no leaks or sensor issues, replace the HC adsorption catalyst.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause increased emissions and potential failure of an emissions test. It is not immediately dangerous, but should be diagnosed and repaired soon.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Replacing the HC adsorption catalyst can range from $200-$600 depending on the vehicle and labor rates.