Summarize the following:
If your code scanner indicated a problem with the vehicle's catalytic converter(s), you'll likely need to replace them to solve the problem. You can find the catalytic converter on the exhaust piping beneath the vehicle. It will be wider than the surrounding pipe and often covered with a metal shield. In some vehicles, you can remove the two bolts in the flange on either side of the catalytic converter to drop it from the vehicle. In others, you'll need to cut them out with a hacksaw. If you cut the catalytic converter out, slip the new one over the exhaust piping in your vehicle and secure it in place using exhaust clamps to make sure it doesn't leak. Tighten the clamps around the pipe by using a socket wrench to tighten the two nuts on the clamp. If your vehicle uses a flange with bolts instead, make sure to place a gasket between the flanges when installing the new one. You can get the gaskets from your local auto parts store. If the error codes indicate an issue with your mass air flow sensor, locate it by first finding the airbox connected to the intake pipe going into the engine. Just past the box for the air filter, you'll find wiring plugged into the mass air flow sensor. Remove it by unplugging the wires and unscrewing the screws or bolts holding it in place. Clean the mass air flow sensor by removing it and spraying it with carb cleaner, which you can get from your local auto parts store. You can replace the mass air flow sensor simply by plugging in the new one and then securing it using the screws or bolts. A bad camshaft position sensor can cause a reduction in power, poor fuel economy, stalling and more. First, locate it by referring to a vehicle specific repair manual, then stick the probes for your multimeter into the two leads going into the sensor, turn it on, and set it to read resistance (ohms). A reading of zero or "infinite" resistance means the sensor is bad and will need to be replaced. Compare any other readings to the specifications listed in the vehicle's repair manual. If the resistance figures don't match, there's an issue with the sensor and it will need to be replaced. Replacing a camshaft position sensor requires specialized tools and may be best left to certified technicians. If the error codes show a problem with an oxygen sensor in your vehicle, you can locate it by climbing beneath the car or truck and looking for where wiring runs into the exhaust piping. Disconnect the wire pigtail leading to the sensor by unplugging it, then just use the appropriate sized wrench to unscrew the sensor and slide it out. You can purchase a replacement oxygen sensor at your local auto parts store. To install the new one, connect it to the wires and then screw it back into the bung you removed the old one from.
Install new catalytic converters if they're clogged. Clean or replace the mass air flow sensor if it causes an error code. Use a multimeter to test your camshaft position sensor if it causes a check engine light. Put in new oxygen sensors if one has failed.