I replace my forward O2 sensor on my 2000 SSEI based on the code given by an OBDII scanner. After completion my check engine light is still on, does the actual fault code have to be cleared from the computer to reset the light. And if so does this require the scan tool to perform this or will disconnecting the battery cable reset the fault.
Some codes are falsely read by parts puppies and therefore you buy parts that may not fix the issue. As an example when I got a code P0171 Lean Bank 1, I was told to replace the O2 sensor.. when it was reading the exhaust fine and my problem was corrosion on cables.
The majority of codes will clear themselves after 3 consecutive start cycles and that specific test passing. A start cycle is in my experience about a 5-10 minute drive to run through the diagnostic tests.
I fully agree with Bill. You need to get the actual code and the description too if possible. In addition to the possibility that the code was misread or mis-interpreted by the person who advised you, there'* also the fact that for any given single code, there is often a series of diagnostic steps you may have to take to determine the real problem.
On the other hand, you may just have to drive the car through 3 or more cycles to clear the code.