My neighbor 2009 Corolla XRS, 138,000 miles, manual transmission and 2.4 l engine. Runs good but thirsty....not getting good mpg & check engine light is on. Found codes PO 138 (02 sensor bank 1 sensor 2); PO 607 (Control module performance); C1201 (Brake Boost sensor). Replaced 02 sensor, cleaned battery posts, replaced air cleaner, changed engine oil/filter and didn't notice any undue stress on any part of the wiring harness, especially near the 02 sensor. Vehicle also has a new MAF sensor. Still getting PO 138 check engine light and poor mpg....runs good. No other codes. Have run out of ideas. Need help.