If you have a factory warranty, you should go to the manufacturer to get the part - as they will have to install it for free. Otherwise, you can go to Napa Auto Parts.
You can find and exhaust system diagram for your 2003 Toyota Camry at most Toyota dealerships. Many local libraries will have Toyota service manuals with the exhaust system diagram.
Start at the engine and follow the exhaust system toward the rear of the car. You willl find all the O2 sensors as they are all screwed into the exhaust system.
O2 sensors are always located on the exhaust system.O2 sensors are always located on the exhaust system.
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under the car
what is bad exhaust system?
Exhaust system brackets are used to hold the exhaust system in place
Screwed into the exhaust system. Follow the exhaust system from the engine rearward and you will find the oxygen sensor or sensors if it if it has more than one.
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You will find an exhaust on a car
The exhaust valves are the hottest component of the exhaust system of an internal combustion engine.