I bought a used 2001 maxiam 20 aniversary edition bout a year ago and it now has about 160k on it.

I changed the coil packs on it a while back because i was getting misfire. It ran great for a few months and now when i go on the highway and car goes over 120km the check engine light comes on.

I did scan on it and it comes up with P138 and P139 and points to H02S2-B1

So do i replace the rear O2 sensor or look at other posible causes like MAF?

Also if i do have to replace the rear 02 sensor what is the BOSH part number that i need for H02S2-B1? I seen afew different ones on some of auto parts sites i checked out so far.

is it Bosch 13374 downstream right or 15225 rear downstream

If i clear the 2 codes i dont see it again but can always make the check engline light come on when i hit 120km or higher on the highway. Never comes up in city driving.

Thanks. I have picked up alot of great info from the forum so far and hope to contirbute to it as i deal with problems on my own maixmia