I am getting the following code from P0174.

I am getting the following code from P0174, P0171 & P1512; the engine light is on. The mechanic wants to replace an oxygen censor. P1512 points to MTIA - mechanical failure. That thsi mechanic replaced last December. He claims it needs an adjustment which he must do together with the replacemnt of the oxygen censor. I hardly undrestand any of this. Is the mechanic correct? Thank you
Ben