Po 131 po171 obd2 codes on 04 kia sorento... indicates o2 sensor ? whish one and where

The problem may not necessarily be a bad O2 sensor. An incorrect air fuel mixture may also trigger this error.

To see if the air fuel mixture is right you may have to check the ignition for bad plugs or coils. Check the vacuum hoses to and from the engine for leaks, cracks or loose connections. Check also the timing. Inspect the throttle body or the actual intake manifold for build up of dirt. A bad injector could also be the culprit.

The error code Po131 is for the sensor before the catalytic converter. Inspect the cables and the socket of the sensor. Check also for leaks in the exhaust.