P1131 and P1151 are normally worn out upstream (not downstream) sensors.
If you replaced any downstream (after the pre-cat) seansors due to these codes, you wasted your money.
The scantool will clear the codes, but will not clear the fuel trim tables that will keep the mixture either too rich or too lean (depending on the failure mode of the original sensors).
Because of this, it is necessary to disconnect battery power from the computer for a long enough time for the internal keep-alive power to discharge.
Steve
