You need to check two things.
First, there is a heat shield on top of the front of the motor where the o2 sensor you already replaced is. It's got (4) 12mm bolts. Remove it and check the exhaust manifold (big thing you put the o2 sensor into) for cracks. If there are any cracks, you'll get o2 sensor codes. Replace the manifold.
Second, if the manifold is fine start the car and listen to the exhaust pipe under the engine for leaks. Or if you already know the exhaust is loud... that's gonna do it too. A leaking exhaust pipe on an Accent will set secondary o2 sensor codes.
SHOULD you try to change it yourself, you will need a 7/8" wrench, and a new o2 sensor, or flex pipe, or manifold depending on what's broke. Do NOT touch the tip of the new or old o2 sensor to ANYTHING when you take it out or install it or it will be ruined permanently. Run the car until it's at it's normal operating temperature. Raise the vehicle, and take the o2 sensor out of the car (see below to understand which one) using the 7/8" wrench or if you got fancy and bought an 02 sensor tool... use it.
Replace whatever parts are bad (manifold or pipe) or just replace the sensor you need. Then restart the car and take it to a parts store and have them clear the code. The code (and check engine light) won't return right away, it usually takes a few days. If you did everything right you should be good. If not, it's not a terribly expensive job to have done and by now you should be able to explain to them what's wrong based on what you found when you looked at the car. Just tell them everything you checked and what you saw.
Education: I'm not sure where that half baked answer about o2 sensor 1 being near cylinder one came from but here's the real deal.
Sensor 1 is always BEFORE the catalytic converter
Sensor 2 is always AFTER the catalytic converter
Bank 1 and Bank 2 refer to which SIDE of the exhaust on 6 and 8 cylinder engines. Bank 1 is usually left side, Bank 2 is usually right side.
So... O2 sensor B1S1 refers to the O2 sensor BEFORE the converter on the LEFT side of the motor.
B1S2 = Bank one, sensor two. If you have a four cylinder, you only have one bank. If you have a 6, 8, 10, 12 cylinder, bank one has the number one spark plug in it. Bank one is also the closest to the front of the engine, i.e., closest to the belts. Sensor two is always the down stream, post cat, after the cat, sensor. This sensor only has one job, to test how well the catalitic convertor is working. It has no other purpose. I have 21 years of experence and I have taught at the "Harvard" of mechanic schools in the world. These normally give off one oftwo codes, catalist efficeincy and O2 Heater failure. The cat eff code does not indicate that the sensor is bad. It is telling you that your cat is not performing up to par. Check you cat with a parometer (Heat detection gun). The temp after the cat should be at least 100 degrees F higher than when it went in, i.e. 900 before = at least 1000-1100 after. If you don't have that, the cat is bad. If the heater is bad in hte O2, which happens a lot, the O2 should be changed with the exact match. Please don't settle on a generic fit.
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Sensor 2 is supposed to be after the cat if you only have two sensors on that exhaust.
If you have another sensor between the one that you changed and the one after the cat, then it will be that one as the one after the cat will be called Sensor 3.
Check engine light on obd code P1127.
I am female and have an 2002 Audi A4 1,8T the O2 sensor needs to be replaced in bank 1. Is this a crisis and should I sell it or is it worth the fix? mi 98,000 in excellent condition though.
Bank 1 is the side that number 1 cylinder is on. Sensor 2 is the one after the cat.
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