Hey Guys,

My 08 V8 (117800km) starting giving me the P2195 and P0138 codes (plus check engine light, trac off and VSC off).

1) Checked with scan tool B1S1 (drivers side before cat) Air/Fuel sensor stuck high voltage lean. Also P0138 indicating rich after cat on B1S2.

2) Changed out B1S1. (Learned hard way to use quality O2 socket. Snap-On SWR2 worked flawless and was 50 bucks. NAPA tool broke and almost stripped old sensor)

3) Starting getting codes P2195 & P0171 and fuel trim was WAY TO HIGH. (40%+). Now running extremely rich (checked sensor was black with carbon when I pulled to examine and exhaust stunk of raw fuel). Voltage was 4.5V+ B1S1 Indicating lean how could this be?

4) Cleaned MAF sensor, disconnect battery to reset engine fuel trims. Start again bang new sensor on B1S1 cleared up, fuel mileage around town as indicated went from 17-19 l/100km to 11-13 l/100km.

What was interesting is that the new O2 sensor appeared faulty however the MAF was showing a much larger air volume that actual. The ECU was tricked into thinking things were lean based on the air volume so it was going full on the fuel (smell confirmed this right away).

In the end truck works fine no codes all OBD2 readiness monitors are good. Gas mileage is up and the B1S2 and B2S2 sensors match. (no killed cat)

Hope this helps someone else out.

Netwon