I would like to know how many o2 sensors are in a 2003 jetta 1.8t gas.

have your o2 sensor checked. if your sensor goes bad it will tell cpu that your not getting fuel and it will continue to dump fuel to injectors or throttlebody

O2 sensor as in lambda sensor in the exhaust you can only get 4 or 5 pin and I would imagine it been a 4 pin as its pre cat . I would buy a OE one

your O2 would be the next thing to check

It sounds like either the mixture is bad or you need a new 02 sensor. If you have never replaced the o2 sensor I would get that done anyway. Next I would get a general tune up and have your throttle body cleaned.

Yes your o2 sensor could do this, it's most likely the closest one to the motor, the first one that is coming from the engine. That is the one that reads the exhaust gas, it then tells the computer how much gas to mix in with the air. It also could be your MAF(mass air flow sensor) connect to your intake.

*PS I have the same motor, wouldn't hurt, might get better MPG.

Its a computer controlled motor so yes if one thing gives it a bad reading the cpu will try to counter the issue and give to much gas or not the right amount of air to the intake... Just from what i have happen to me I would look for a leaking vaccume line or a clogged cataltic converter befor replaceing the sensors both can give a false o2 reading on the computer and seem to be more common on most cars..

may be both o2 sensor

this is the O2 sensor that is just off the engine in the exhaust and before the catalytic converter, sensor one bank one, u only have one bank of cylinder

The error codes you have are for the O2 Sensors. There is one before and after the catalytic converter. It is usually the first O2 sensor that is the problem because the second sensor is used just to verify the converter is working. The O2 sensors are usually $60 to $130 dollars depending on the type your vehicle uses. they are located on the downpipe on the exhaust system and the other is locted after the catalytic converter on the exhaust system. The O2 sensor not working will cause you gas mileage to be reduced because the car's computer will run the fuel mixter rich.

The EPC ( Electronic Power Control) light comes on because there is an problem with the engine. I would take it to your local dealer or part store and have them hook a scan tool up to it and read the codes. This will give you a code or codes that identify what is wrong with your engine. The part store does not charge for this service, the dealer does. If you have a mechanic that you trust, I would take it to them. Hope this helps.