Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Catalytic Converters
The catalytic converter is located in the exhaust system prior to the muffler. The catalytic converter is an emission control device added to the gasoline exhaust system to reduce hydrocarbon and carbon monoxide pollutants from the exhaust gas stream.
There are 3 types of catalytic converters: Conventional Oxidation Converters (COC), 3-Way Catalyst (TWC) and dual bed catalytic converters which are a combination of both the above mentioned. All catalytic converters are of 2 designs: non-serviceable, honeycomb-type block, or a small canister containing catalytic beads.
Both converters contain a base material of alumina impregnated with platinum/palladium, while 3-way catalysts in addition to this also contain a material coated with platinum/rhodium. Both converters reduce hydrocarbons and carbon monoxide, while the TWC also reduces oxides of nitrogen.
On some models, a TWC is used in conjunction with a COC both contained in the same canister. Working in conjunction with this, there often is an air injection pipe. This pipe injects air between these 2 beds to help further oxidize the exhaust gases. This is called a dual-bed converter. See Fig 1 .
On all other dual bed converter models, the first converter (3-way) in the exhaust system reduces hydrocarbons (HC) and carbon monoxide (CO), but mainly deals with oxides of nitrogen (NOx). In the second converter (oxidation type), with extra help from the air pump, reduction of hydrocarbons (HC) and carbon monoxide (CO) takes place.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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