Core Function
Catalytically convert the three main harmful substances in engine exhaust gases:
Carbon monoxide (CO) → Carbon dioxide (CO₂)
Hydrocarbons (HC) → Water (H₂O) and carbon dioxide (CO₂)
Nitrogen oxides (NOx) → Nitrogen (N₂) and oxygen (O₂)
Structure and Principle
Carrier: Honeycomb-shaped ceramic or metal structure, with the surface coated with catalysts (such as platinum, palladium, rhodium and other precious metals).
Catalytic reaction:
Reduction reaction: Treat NOx, decomposing it into nitrogen and oxygen.
Oxidation reaction: Treat CO and HC, converting them into carbon dioxide and water.
Working conditions: High temperature and appropriate air-fuel ratio, with oxygen sensors for control.
Common causes of faults
Fuel/oil issues:
Low-quality fuel containing sulfur, lead, or oil combustion residues can cause the catalyst to become "poisoned".
Carbon deposits blockage: Long-term low-speed driving or incomplete fuel combustion can lead to blockage.
Physical damage: Bumping or high-temperature sintering can cause the carrier to break.
Abnormal mixture: Imbalanced air-fuel ratio (such as fuel injection failure) can cause the catalytic converter to overheat and fail.
Symptoms of the malfunction:
- A pungent odor in the exhaust and excessive emissions.
- Reduced engine power and increased fuel consumption.
- Warning lights on the dashboard (such as an OBD indication of low catalytic converter efficiency,P0420,P0430).
Maintenance suggestions:
Use genuine fuel and low ash engine oil to prevent impurities from damaging the catalyst.
Regularly inspect the ignition/fuel injection system to prevent overly rich mixture or misfire.
After long-distance driving, run the vehicle at a moderate high speed to help burn off carbon deposits.
Avoid driving through water or dragging the undercarriage to prevent damage to the carrier.
Replacement cost
The original factory catalytic converter is relatively expensive (hundreds to thousands of dollars) due to the presence of precious metals.
OEM parts or repair solutions are less costly, but compliance should be taken into account.
Note: If the vehicle fails the annual inspection due to a failed catalytic converter, it is recommended to first check the oxygen sensor or clean the carbon deposits, as a direct replacement may not be necessary.