Rich exhaust smell

My 2000 Grand Caravan has recently exhibited a gas-rich exhaust smell. I've maintained the car and recently replaced the air filter. I'm wondering if the problem could be due to a clogged pcv valve or perhaps degradation of the O2 sensor.

I checked for fault codes which showed 23 & 55. I'm not sure if these faults are start and stop of fault codes or are actually legitimate problems.

Thanks in advance...........

Everything I have been able to find indicates that the 23 code means that the incoming air temp. sensor is bad. The 55 means end of codes. If the air temp sensor is not reading correctly it could tell the computer to send too much gas to the engine thus giving you the gas rich exhaust smell.

Thanks. Any idea where the Air Intake Temp sensor is located? I looked but couldn't find it. Is it near the intake manifold or in the intake air stream nearer the air filter?

It should be in the air stream somewhere either in the air cleaner box or in the piping leading to the throttle body. Look for any wires connecting to this area that should be it.