01 jetta 1.8t,cel PO172 too rich,help

so got a check engine lite on,where should i begin diagnosing.code is po172,system too rich bank1.the car runs perfect.o2 sensor maybe?any help is appreciated..

First question is if you had any service or modifications done to the car recently?

hey,thanks for replying,only thing was oil change,and replace leaking plastic water hose...used 10/30 valvoline,would not using right oil set a code?(non-synthetic).

o,yea..car is completely stock.

A dirty MAF Sensor, loose plug wire, dirty/broken spark plug, dirty fuel injectors, vacuum leak, could all be a cause as well as a faulty o2 sensor. If your vehicle has high mileage a total tune-up is where i would start.
1. Spark Plugs and Wires
2. Fuel Filter
3. Air Filter
4. Fuel Injector Cleaner

right on!thanks for your valuable help,im replacing the timing belt this weekend so I will do the tune-up then...I will let you know how it goes! thanks again for your help.talk soon.