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.
Description & Operation: Notes
Catalytic converter(s) is located in exhaust system in front of muffler. It is a stainless steel, muffler shaped, device that reduces exhaust emissions by changing toxic gases into less harmful ones.
There are three types of catalytic converters: Conventional Oxidation Converter (COC), Three-Way Converter (TWC) and Light Off Converter (LOC). Catalytic converters may be one of 2 designs: honeycomb-type block or small alumina beads.
Even though converters contain base material of alumina, COC is impregnated with platinum/palladium and TWC contains material coated with platinum/rhodium. While converters reduce hydrocarbons (HC) and carbon monoxide (CO), TWC also reduces oxides of nitrogen (NOx).
On some models, TWC is used in conjunction with COC (fresh air is introduced between converters to aid in oxidation of gases), this is called a dual-bed converter. See Fig 1 .
On some models, first converter in exhaust system is a LOC. This is a single-bed converter designed to control exhaust emissions during engine warm-up.
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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.