So I now have two codes for o2 sensors .. P0137 and p 0157 bank 1 sensor 2 and bank 2 sensor 2. I have no exhaust leaks. What is the common cause for both of these codes to trio at the same time?

 

Honestly it means they are both failing.

 

Only good for about 100k

 

Depends on the exact definition of the code, if the upstream O2 sensor (sensor 1 on each bank) is running the engine rich it will trigger a code in the downstream sensor. So before you waste money on the downstream sensors, replace one or both upstream O2 sensors (both especially if code shows both upstream are bad) and reset computer and that should solve your problem. Replace down stream after getting new upstream only if a code still appears for the downstream after compuster is reset. Just to be clear, the upstream are the ones closest to the engine.

The downstream O2 sensors do nothing but trigger a check engine light to alert you that the catalytic converter emissions are too high and to of course alert you that the sensor itself may be failing. They have ZERO effect on the way the engine runs.

You're dealing with a sensor issue not a leak, believe me, my passengers side manifold leaked pretty good out of #8 cylinder enough to turn the back of the head carbonized and it also leaked along with my cat cracking & breaking right at its nose just inches away from the O2 sensor on the same side as my leaky manifold and NEVER threw a code the whole month it took my dad to find time to weld it with a stick welder (we don't have a mig/tig welder). The cat crack opened up a gap about an 1/8th of an inch on the bottom of the cat...so if your system looks vaguely good that isn't the problem ;-)