Front o2 sensor is needing to be replaced

Too Lean on which Bank of the Motor?

To have a lean O2 Code --you could have a rich fuel
condition & the pcm drove the fuel trim lean

Next you could have a vacuum leak-in the intake or exhaust system

Third you could have a failed O2 Sensor

Front or Upstream Oxygen Sensors get replaced at 100,000 miles

The front sensors are on the exhaust pipe between the motor &
the converter.

Will need a long handled flex head O2 Sensor Wrench

You do not change any O2 Sensors based on an OBD2 Code

You change sensors,front 2 only at 80,000 to 100,000 miles

You use a 22 mm wrench or special O2 socket.
Some veh use a diffent size

Easy job,they are in the front of the converter
or pipe before it

The number of wires with be year and application
specific

You get an OEM Type, NOT a universal cut and splice

5 minute job per side

Yes it can be determined by the DTC (Data Trouble code). If the DTC is P0420 (catalyst system efficiency below threshold Bank-1) then the side of the engine with the #1 spark plug and cylinder is always Bank-1, and the O2 sensor that monitors the catalyst efficiency is usually after or (post) of the catalytic converter.

The #1 cylinder is located at the front spark plug on the right or the passenger side of the vehicle, so Bank-1 is on the right side of the vehicle, and the O2 sensor that monitors the catalyst efficiency should be located after or (post) of the catalytic converter. It would be the post right O2 sensor.

There is also the possibility that the catalytic converter is actually starting to fail, and if changing the O2 sensor and clearing the DTC does not solve the problem them the catalytic converter is most likely faulty.

code P0135 heated O2 sensor bank 1 sensor 1 , heater circuit ( front O2 sensor driver side ) replace O2 sensor

code P0741 this is a transmission code TCC ( torque converter clutch ) stuck off. most likely you need to replace the TCC switch.

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.

IT IS IN THE SIDE OF THE ENGINE BLOCK, SCREWED INTO THE WATER JACKET OF THE BLOCK

I just got done replacing the O2 sensors in my 99 Cougar due to throwing a P0135 malfunction code. There's 3. Facing the engine there's one in the front coming off of the front header, which is easy to get to. Another more tricky one if between the engine and the fire wall on the rear header pipe. The third is under the vehicle behind the transmission pan on top of the exhaust. In order to replace the O2 sensor near the fire wall you will need to remove the 4 retaining bolts for the ECM module and move it out of the way. Additionally you will need to remove the 2 retaining nuts for a wiring harness that is seated below the ECM module. Pay close attention to the connectors because the front and under vehicle O2 sensors have round connectors the one near the firewall has a squared connector. I was able to replace all 3 by myself in approximately 35 minutes. If your throwing a O2 heater malfunction code it is most likely going to be the sensor near the firewall. make sure that you know someone with a code reader so the code can be cleared. If you're do for an emmissions inspection be sure to put at least 40 miles on the new O2 sensor with different types of driving (e.g. highway, coasting, decellerated turns and rapid acceleration). Gotta love project cars for your kids!!

Yess bad EGR valve

Did you support the vehicle on a lift and run it, with wheels engaged?
Since you have changed all the usual suspects, Have you checked the hub bearings? It could be that, or, something stupid like a backing plate hitting a rotor.
Regarding the cat/o2 sensor thing. Cats do go bad, so do o2 sensors but, generally a code for an o2 sensor indicates a problem elsewhere, causing a lean or rich condition in the exhaust pipe, beyond the parameters of the o2 sensor. PS: check warranty on cat. generally it runs longer than many other components.

There are two O2 sensors on the Lanos. The first is located on the front of the engine block, right between the two cooling fans. You need to remove these two fans and the heat shield to remove this sensor. The second sensor is located in front on the catalytic converter, passenger side, just in front of the front tire, and is easily replaced.