Fig. 59: Identifying HO2S Locations (In-Line Engines)
Courtesy of FORD MOTOR CO.
Catalytic Converter
A catalyst is a material that remains unchanged when it initiates and increases the speed of a chemical reaction.
A catalyst will also enable a chemical reaction to occur at a lower temperature. The catalytic converter assists in
controlling the concentration of exhaust gas products released to the atmosphere. It contains a catalyst in the
form of a specially treated ceramic honeycomb structure saturated with catalytically active precious metals. As
exhaust gases come in contact with the catalyst, they are changed into mostly harmless products. The catalyst
initiates and speeds up heat producing chemical reactions of the exhaust gas components so they are used up as
much as possible. For additional 3-Way Catalytic (TWC) converter information, see 3-WAY CATALYTIC
CONVERTER .
Light Off Catalyst
As the catalyst heats up, converter efficiency rises rapidly. The point at which conversion efficiency exceeds 50
percent is called catalyst light off. For most catalysts this point occurs at 475-575°F (246-301°C). A fast light
catalyst is a 3-Way Catalyst (TWC), that is located as close to exhaust manifold as possible. Because light off
catalyst is located close to exhaust manifold it will light off faster and reduce emissions quicker than the catalyst
located under vehicle. Once catalyst lights off, the catalyst will quickly reach maximum conversion efficiency.
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline