as so0on as my car reaches operating temp, the ck. eng light comes on, the oxygen sensors are 2 yrs old?

Answer 1

If your car is 1995 or older, you can most likely retrieve the diagnostic codes with a paperclip and read them as "flash" codes on "Check Engine" light.
If it is 1996 or newer, you will need to depend on the grace of they nice fellows at the local discount parts store to read them for you.
When you have them in hand, follow proper DIAGNOSTICS and subsequent repair procedures.
Do NOT assume that a code for an oxygen sensor means to replace the sensor. It means that there is a fault or failure in that circuit, or a related system, which also includes several connectors, wires and junctions. Check out the circuit and system indicated, and replace parts ONLY when it is clear that the PART is the cause of the fault or failure.

Good Luck

Answer 2

you need to borrow a code scanner, it could be something as simple as a loose gas cap or another o2 sensor, they might have 4 :)