I have a 2002 ford focus and the emission system light came on what does that mean?

I have a 2002 ford focus and the emission system light came on what does that mean? - 1

It's usually the oxygen sensor, aka lambda sensor, that is faulty. Or it may be a failing catalytic converter (expensive). It is worth getting the car up to full working temperature and blasting it down a motorway for a few minutes. This burns off residual carbon from the sensor, which may be giving a false reading. If that fails pop the car into a Ford Dealership and ask them to diagnose the fault by reading the car's fault codes.

Bad EGR

You need to get the fault code read before you spend any money on anything. You can get a code reader lent to you at some auto parts stores like Autozone. Until you do that you are wasting your time. It could be as simple as an improperly replaced gas cap.

The code(s) producing the light must be read to narrow down the suspects. A hint, though - if the code is P0171 (system too lean) check the PCV hose where it makes the sharp bend at the manifold, against the firewall. In that era Focus it loves to tear on the outside of the bend - you would feel it with your fingertip. The hose has different size ends and must be bought from Ford.

Hi it is not just the emission light. That is the engine and transmission service light. So time to be spending some money getting it fixed.

It could mean a lot of things. Go get your car scanned at an auto parts store like AutoZone or O'reilly. They do it free of charge and can shed a little more light on it.