1 FMF

iTrader: (1)

i can reliably cause P0137 to trip on my truck, 2006 sierra 8.1L.
it only happens under this condition:
- drive for at least 30 min on highway above 60 mph.
- stop, turn truck off, restart within an hour, get back on highway within a minute and do 60+ mph.
- p0137 trips after 2-3 minutes while on highway, never any kind of performance hit.

otherwise i can drive the truck rest of the year to and from work and never have this code trip. at first i though it had something to do with getting gas and having a full tank, but i verified it with less than 1/2 tank i did everything the same on a long trip but didn't get gas and code still tripped.
i did a trip up and down the east code 2 years ago and had this happen. cleared code, been fine since doing local driving and minimal highway trips. did same trip down east code last week and had same thing happen with p0137.

p0137 = bank 1 sensor 2, means the O2 oxygen sensor's voltage remained low for longer than 2 minutes.

any ideas?
i'm thinking of swapping rear o2's from left to right,
also considering putting 2 new front o2's in and moving fronts to rears,
truck now has 90k miles