Oxygen sensors getting a P0155 error code?

Here is a guide to help you step by step with instructions in the diagrams below to show you how on your car.

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

Bank one is where cylinder # 1 is
bank two is where cylinder # 2 is
good luck

Hello

Right exhaust, second sensor. Bank 2 is on the same firing side as cylinders 2, 4 and 6 which looks like the drivers side. Bank 1 is always on the same side as #1 cylinder.

They cost about 70 bucks on average per o2 sensor, there is one before the catalytic convertor, that is for sure, usually on the exhaust manifold, but sometimes on the piping, and there may be one after the convertor but not always.

Forgot to mention.

The second o2 sensor, one after the convertor, has nothign to do with engien performance, it is used to measure the catalytic convertor's efficency to tell you if its good or bad.

So if you think replacing the second one will give you better gas mileage, you will be wasting the money.

Thanks for the additional information, is it the same litre engine?

Heated Oxygen Sensor (Left Bank) (Front). In left exhaust pipe, below exhaust manifold.

Heated Oxygen Sensor (Rear) (Left Bank). Underside of vehicle, rear of catalytic converter.

Heated Oxygen Sensor (Rear) (Right Bank). Underside of vehicle, rear of catalytic converter.

Heated Oxygen Sensor (Right Bank) (Front). In right exhaust pipe, below exhaust manifold.

Hello,

Here is a guide that will help you see what you are in for when changing out the oxygen sensor.

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

Here is the location of the sensors in your car (Below)

Please let us know if you need anything else to get the problem fixed.

Cheers, Ken

Hello, bank one is the right side of the engine. first I show several different Montero 4WD models. I am going with Sport ES. The truck has 4 Oxygen sensors on it. I have attached the pics. You really need to know what the codes are. There are a couple of technical service bulletins out, but again, need to know the correct model of the vehicle and what the codes were. Stop by Auto Zone or O'Reilly's. For free they can pull the codes and if it is an O2 sensor, it will tell you what position. I would be more concerned with what sensor they changed and what code they saw. As for the oil. . .. . .well, there is a slim possibility. It does raise the question that if it were that new it should be more durable..........it does kind of make you say. These are heated and any fluid that would interrupt the connection may cause a problem. It is possible you had two sensors go bad. Let's check the codes first. Where is the oil coming from would be my next concern especially if it was running down the cable. Let us know

One thing that can cause this is a leaking head gasket, or other contamination. If the anitfreeeze comes in contact it will cause problems. Also other things that should be checked is for vacuum leaks which will give a faulty reading. And dont forget to check the air filter which will restrict air flow.

You can try using it, but if it triggers an oxygen sensor code you're right back to the OEM part