I have a 2002 nissan maxima with an engine code PO1038 02 high voltage lean bank 1, 2
What do this means can anybody please help

Do you mean a P0138? That sensor is after the converter to monitor the converter efficiency.
This often means that there is something causing the fuel mixture to have too much air before the converter.
Frequently, that is an engine vacuum leak between the Mass Air Flow Sensor (MAF) and the engine. Including along the intake seals.
Diagnosing this will be very hands-on. A current scan tool may even be required.
Some techs can find these quickly, though other times the problem is more difficult to pin-point.