How to clean a Catalytic Converter: 2025 Complete Guide

The catalytic converter is one of the few components in the automotive industry that combines environmental mission, high value, and potential difficulty. Although it is a "mobile treasure" in the eyes of thieves, it quietly lurks beneath your automobile and can purify emissions.

However, many automobile owners are faced with a replacement plan that costs thousands of yuan when the engine light abruptly turns on and the diagnostic tool ruthlessly displays code P0420 (catalyst system efficiency below threshold). But hold on, before you sign that costly repair bill, remember that in 2025, we have more intelligent and varied options.

Cleaning the catalytic converter is no longer a straightforward "wash and be healthier" task, but rather a planned endeavor focused on diagnosing the underlying cause of the malfunction and implementing systematic repairs. While it is not a universal solution, it can potentially reduce replacement costs by up to 90% and restore your vehicle to its former condition under the right circumstances.

What do catalytic converters do​?

The catalytic converter is the core component of the automobile emission system. It carries out oxidation-reduction reactions at high temperatures to convert harmful gases into harmless products.

• Oxidation reaction of carbon monoxide (CO): Under the action of catalysts platinum (Pt) and palladium (Pd), the toxic CO is oxidized into harmless carbon dioxide (CO₂).
• Oxidation reaction of hydrocarbons (HC): Under the action of catalysts platinum (Pt) and palladium (Pd), hydrocarbons are oxidized into carbon dioxide and water vapor.
• Reduction reaction of nitrogen oxides (NOx): Under the action of the catalyst rhodium (Rh), NOx is reduced to nitrogen (N₂) and oxygen (O₂), thereby eliminating the harm of nitrogen oxides.

Therefore, it is one of the key technologies for modern automobiles to achieve the China VI/Euro VI emission standards.

Why does the catalytic converter need to be cleaned?

1. Excessive exhaust emissions and failure to pass the annual inspection: When the catalytic converter becomes blocked or fails, the concentration of CO, HC, and NOx in the exhaust stream increases dramatically. This not only pollutes the air but also causes the vehicle to fail its annual environmental inspection.

2. Blockage results from the accumulation of pollutants and carbon deposits: Not all of the fuel is consumed during the engine's combustion phase. Along with the exhaust gas, the remnants of incomplete combustion—such as dust, metal oxides, carbon particles, and oil stains—will enter the three-way catalytic converter and stick to the honeycomb carrier. When accumulated over time, these deposits will:

• Block the catalytic channel and restrict the flow of exhaust gas;
• Reducing the contact area between the catalyst and the exhaust gas will reduce the reaction efficiency;

• Increased exhaust back pressure causes the engine to work harder.

3. Catalytic layer surface poisoning and aging: The catalytic converter's core catalytic material is a very sensitive precious metal (platinum, palladium, and rhodium). The catalytic layer will become "poisoned" and lose its catalytic function when certain impurity elements (such as sulfur, phosphorus, lead, zinc, etc.) in fuel or engine oil chemically react with it. For example:

• The use of leaded petrol will permanently disable the catalyst.
• Oil burning in the engine can cause phosphorus and zinc deposits to cover the catalytic surface;
• Long-term high temperature or idling driving will cause the catalytic layer to sinter and age.

4. Increased exhaust back pressure has an impact on engine performance: When the catalytic converter is blocked, the exhaust gas cannot be discharged smoothly, causing the exhaust back pressure to rise. This directly affects the engine's intake air volume and combustion efficiency.

5. Avoid expensive replacement expenses: the cost of replacing a three-way catalytic converter is complicated, and the original model typically costs between 3,000 and 8,000 yuan, with some versions costing tens of thousands of yuan. Regular cleaning can significantly prolong the service life and is only a tenth of the price of replacement.

How to clean a Catalytic Converter step by step

First method: without disassembly (recommended)

This is the most common and safest method, suitable for light blockage or carbon deposits.

Operation steps:

1. Add the cleaning agent: Add the Biaobang catalytic converter cleaner to the fuel tank (according to the instructions, generally add one bottle for every 50L of fuel).
2. Normal or high-speed driving: After the engine is preheated, drive at medium to high speed for 10–15 minutes to allow the cleaner to pass through the catalytic converter with the exhaust gas and decompose the internal carbon deposits.
3. Observe the effect: If the power is restored and the odor of the exhaust gas disappears, it indicates that the cleaning effect is obvious.

Method 2: Disassembly and cleaning (suitable for severe blockage)

If the vehicle has a significant power drop or excessive back pressure, it is recommended to remove the catalytic converter for deep cleaning.

Operation steps:

1. Cool the engine and lift the vehicle: Ensure the engine is completely cool and use a jack to support the vehicle safely.

2. Remove the catalytic converter: Use a wrench to remove the fixing bolts and carefully remove the catalytic converter.

3. High-pressure water flushing: Use high-pressure water to flush the inside of the catalytic converter from the opposite direction to remove carbon deposits and impurities.

4. Drying and reassembly: Allow to air dry or tumble dry on low heat before reassembling.

FAQs

Q1: What should I do if the catalytic converter is blocked?

If the blockage is slight, try cleaning it; if the blockage is serious or the pipe is broken, it must be replaced.

Q2: How often should the catalytic converter be checked?

It is recommended to check it every 30,000-50,000 km or immediately when abnormal exhaust gas is found.

Q3: Can cleaning the catalytic converter restore all of its functions?

Cleaning can remove carbon deposits and mild blockages, but cannot repair internal ceramic damage. Severe damage must be replaced.

Q4: Is it safe to use detergent?

Choose a reputable brand, follow the directions, and avoid harming the catalytic converter or emission system.