2006 Elantra CEL STILL on after O2 bank 1 sensor 1 and flex pipe replaced

Usually these are located on the exhaust manifold or just below the exhaust manifold and you should be able to see it in the engine bay. On V6 engines there will be one sensor on each of the 2 exhaust banks.
You will probably need to remove the engine cover to see the sensors on your exhaust.

If someone told you to replace these because you got a particular fault code I would be wary. A decent scan tool and basic diagnostics can show if the 02 sensor is working or not. Some faults often blamed on an 02 sensor are not due to faulty sensors.

Probably replaced a good sensor. This codes could be from a bad sensor, a vacuum leak, or an exhaust leak before the sensor.

It has two sensors. Bank 1 Sensor 1 is inside the engine bay under the metal heat shield on the front of the engine. Check out NTK sensors online. The one you need will be a 4 wire sensor. The NTK part number is 24588.

Possible O2 sensors:

P2270 O2 Sensor Signal Stuck Lean Bank 1 Sensor 2
P2271 O2 Sensor Signal Stuck Rich Bank 1 Sensor 2
P2272 O2 Sensor Signal Stuck Lean Bank 2 Sensor 2
P2273 O2 Sensor Signal Stuck Rich Bank 2 Sensor 2
P2274 O2 Sensor Signal Stuck Lean Bank 1 Sensor 3
P2275 O2 Sensor Signal Stuck Rich Bank 1 Sensor 3
P2276 O2 Sensor Signal Stuck Lean Bank 2 Sensor 3
P2277 O2 Sensor Signal Stuck Rich Bank 2 Sensor 3
P2278 O2 Sensor Signals Swapped Bank 1 Sensor 3 / Bank 2 Sensor 3
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This is Bank 1 (closer to the dash panel) Sensor 2 (located after the catalytic converter).

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Note: A malfunctioning front oxygen sensor may cause fuel trim codes to set.

1. Several Diagnostic Trouble Codes use specific terminology to refer to sensor location. The illustration and key below explain the following terms:
2. Engine BANK Bank 1 is closer to the dash panel, (also referred to as RH or right hand). Bank 2 is closer to the radiator, (also referred to as LH or left hand).
3. UP Refers to Sensor 1 or "front sensor". It is located closer to the exhaust manifold and before the catalytic converter.
4. DOWN Refers to Sensor 2 or "rear sensor." It is located after the catalytic converter.
5. The following examples show how to interpret oxygen sensor terminology:
6. B1/S1 = Bank 1/Sensor 1 = Dash panel side, BEFORE the catalyst or "upstream"
7. B2/S2 = Bank 2/Sensor 2 = Radiator side, AFTER the catalyst or "downstream"

P2626 O2 Sensor Pumping Current Trim Circuit/Open (Bank 1 Sensor 1)

I'll sure this has to do with a faulty O2 sensor. This sensor is usually located around the header of your car, or down more on your exhaust.

Try disconnecting your battery for 30 mins, hook it back up, and start your car again. This will erase the error. See if it comes in again.

Hope this help (remember rated this post).

they are the only sensors that are plugged into the exhaust system. follow exhaust from engine u will spot them. replacement tip- get exhaust warm 120 F or so to help with replacement. cold exhaust makes it much harder to replace. if u have a 6 cylinder engine there may be more then 2 sensors

P1166 O2 Sensor - controller adaption diagnosis malfunction (bank 1).

Trouble area:

* P1166 is case for HO2S (Bank 1, Sensor 1) Signal line open
* Fuel system (Fuel tank/Pressure regulator/Fuel pump/PSV) failure
* Poor connection to fuel line hose/sealing/cut
* Sealing between purge valve and fuel tank
* Air leakage in exhaust system
* Ignition system (ignition coil, spark plug, cable) failure
* Surge tank and intake port failure

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.

I have a 2001 Elantra, and the Check Engine light keeps coming on. Replaced the o2 sensor, 3 times, and flex pipe was replaced. The engine light came back on...original fault code was P0133............any ideas??

Hi the code P0139 is Bank 1 sensor 2 lambda sensor fault ,possible wiring or sensor fault even if you replace the sensor you need to have the MIL lamp turned off by a Diagnostic machine,it is possible you have another fault such as poor Catalytic converter efficency giving the same fault code ,Would recomend you get the car checked and read the "live" data as the car see`s it to make an accurate diagnosis and cure