Usually with an OHM meter. the book- Chiltons- says what the resistence should be on each. If they fall out of the recommended range, replace them. If you can't do that, then a mechanic will have to do it for you, and troubleshoot it, depending on the symptoms. Good luck.
What sensors? Be specific.
Check for fuel and check for spark before you start looking at sensors.
No
multimeter
There are sensors all over the engine that can turn the check engine light on.There are sensors all over the engine that can turn the check engine light on.
Infared sensors are not very pricey. If you need good price check out Ebay.
You can not reset your oxygen sensors. You can only replace them. To reset the check engine light you will have to get that done by a repair shop with a computor. If replacing the sensors does not repair the problem then check for a vacuum leak.
Then you may want to have a mechanic check it out.
check for the camshaft/crankshaft sensors... where is your camshaft/crankshaft sensors
check cam sensors and crank sensors. coils get their pulse from there
Check
A 2003 Chevrolet Impala typically has four oxygen sensors. There are two upstream (pre-catalytic converter) sensors and two downstream (post-catalytic converter) sensors. The upstream sensors monitor the air-fuel mixture, while the downstream sensors help check the efficiency of the catalytic converter.