p1131 and p1151 codes in 2001 murcury grand marquis, any tech help?

 

Codes indicate both upstream oxygen sensors are stuck running lean. The computer is trying to correct for an overly rich mixture.
What kind of maintenance has been done to the vehicle?
How long has the check engine light been on? Are you in the habit of filling the tank right to the very top ? There could be several reasons for an overly rich mixture, but a little history might help to save some $$$$.