o2 sensor

Bank 1 vs Bank 2 – Sensor 1 & 2 O2 Sensor Location

In Troubleshooting by Magnus Sellén17 Comments

bank 1 vs bank 2

Are you struggling to find out which O2 sensor you actually should replace?

We get a lot of questions about how to locate which O2 sensor is bank 1 and which one is bank 2.

That’s why I decided to write this article to sort it out once for all. It sounds really confusing with all the “Bank 1 Sensor 2 etc” but if you have learned it once, it’s not that complicated.

I often hear about people that replaced the wrong sensors because they did not have the knowledge of which sensor they replaced. After you have checked out this article you won’t do the same mistake!

What is bank 1 vs bank 2?

The engine’s cylinders are often divided into two parts. If you have a V-engine you have one bank on each side of the engine. I hear a lot of rumours about guys that are telling others on the internet which side is bank 1 & 2. The real truth is that you can’t simplify it and say that bank 1 is on the driver’s side or vice versa because different engines can have cylinder 1 on different sides. We drive on different sides also, so it’s just really confusing and misleading to guess which side bank 1 -2 is.

Bank 1 vs Bank 2

  • Bank 1 is the side with the #1 cylinder (Cylinders 1 – 3 – 5 – 7 etc)
  • Bank 2 is the side with the #2 cylinder (Cylinders 2 – 4 – 6 – 8 etc)

To find out how you can find out which side is bank 1 vs bank 2, continue to read down further in the article and I’ll explain how you can find it easily. But I have an inline 6 that is telling me bank 2? You may ask.

That’s why I do not want to tell you a side which is bank 1 & 2. You can have bank 2 on both inline engines and transverse engines (Engines mounted in the other direction). If you know which cylinder that is number 1, there makes no difference if you have an inline or transverse engine. Bank 1 is always on cylinder 1 – 3 – 5 – 7 – 9 – 11 and bank 2 is always on cylinder 2 – 4 – 6 – 8 – 10 – 12.

What is Sensor 1 & 2?

The sensor number is telling us where on the exhaust system the O2 sensor or Exhaust temperature sensor is mounted. The 1st sensor is located closest to the engine and the last is located at the rear of the exhaust system.

Generally, if we are talking about O2 sensors:

Some Diesel engines have a lot of exhaust temperature sensors and it can use Sensor 1 – 2 – 3 – 4 etc. In these cases = Sensor 1 is located nearest the engine and the last sensor in the read of the exhaust system.

How can I find the cylinder numbers?

You can find the cylinder number in some different ways. On some vehicles, you can find the cylinder number stamped on the crankcase cover. If you have ignition cables there are also often numbers on those, but it’s not a recommended method because they can have been replaced/moved to another cylinder before.

The most secure way is either to look if you can find it on the crankcase cover or find it the cylinder order in your service/repair manual. You can also call your authorized dealer and ask them if they have any information about it. You could also try to search the internet for it by searching for your engine code + firing order or cylinder order. If you are not sure, you can ask us a question for free at our homepage.

Mechanic recommendation:

If you have an OBD2 scanner at home, you can make this process a lot easier. If you do not have one and want to buy one, you can check out our review of Best OBD2 scanners.

When you have access to a scanner, you can do this to find out which side is bank 1 and which is bank 2.

  1. Connect your OBD2 scanner and erase the trouble codes.
  2. Make sure that all trouble codes are erased
  3. Unplug one O2 sensor and check the DTC code. You will now see which is bank 1, and which is bank 2.

By using this method, you will also solve any misinformation in the DTC tool and you will be 100% sure that you replace the right sensor.

I have the DTC code P0420 also, which one should I fix first?

The P0420 code can be triggered by a faulty O2 sensor. My recommendation is to troubleshoot the O2 sensor first as it may fix the P0420 code.
Check if you can find any exhaust leaks, which could trigger both the P0420 and O2 sensor DTC code.

If you want more help on how to diagnose the P0420 code, you can check out our P0420 Troubleshooting article.


If your DTC code says:

  • Bank 1 Sensor 1 = O2 sensor located before the catalytic converter, on the side with Cylinder #1
  • Bank 1 Sensor 2 = O2 sensor located after catalytic converter, on the side with Cylinder #1
  • Bank 2 Sensor 1 = O2 sensor located before the catalytic converter, on the side with Cylinder #2
  • Bank 2 Sensor 2 = O2 sensor located after catalytic converter, on the side with Cylinder #2

If you still do have any questions about this, comment down below and I will help you. If you have any other car questions, you are welcome to ask them for free at our homepage.

I hope you enjoyed this article and would appreciate if you checked out our other articles also.

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.

    1. Author

      Often the sensor one and sensor two is different. Check the part number and amount of wires to it. Sometimes you use a wideband sensor for the front sensor and a normal sensor for the 2nd!

      1. Is bank 1 on a Toyato sienna the front behind the radiator or the middle piece with pipes and a curve on it?

  1. Hi sir I’ve had somebody install a bank 2 sensor into my bank 1 sensor port and my car is working poorly will this cause any further problem and will the car work if If I remove the sensor 2 completely and not yet put in the sensor 1

    1. Author

      Is one sensor just hanging in the air or are the sides mixed? If this is the case it will for sure run poorly and light up the engine light. You can’t switch the sensors between the banks, because if you do it will try to adjust the fuel on the wrong bank and cause the engine to run very poorly.

  2. My reader doesn’t specify if it is sensor 1 or 2… any other way to see.

  3. Hi there i have a 2006 ford focus. Engine code is HWDA.

    I have been told bank 2 sensor 2. Could you tell me were this is located.

    The internet tells me the cylinders fire in order of 1-3-4-2. Not sure how true this is but thats all i have found

    Thanks in advance

  4. hiya.

    i have a audi A8 4.2TDI 2014.

    my engine management light has come on With the following code.
    9814- sensor 1 for exhaust temp bank 1 G235
    P0544 00 039 circuit malfunction.
    Can you please tell me or direct me roughly where this sensor might be or even better a part number.
    i have already bought a sensor from audi and had it fitted and it was the wrong one.



  5. So I have a 2006 Jeep Grand Cherokee v6 I’m having trouble locating bank 1 sensor 2 it appears I have 1 sensor on my driver side and 3 sensors on my passenger side any ideas on how to pinpoint the one I need ?

  6. Hi this is William, I appreciate guys like for helping people, I meant your articule on the mattwer is very helpful, thanks a lot.

  7. I have bank 2 way out of whack from bank 1. Thing is it’s only a 4pot. Any chance this is some weird ford thing?

  8. On the O2 sensors what is the difference between UPSTREAM AND DOWNSTREAM

  9. I have a 2001 toyota sienna 6 cylinder.it has 3 catalytic converters.1 one each bank in the front and 1 in the back.it only has 3 o2 sensors.1 one each front cat and 1 behind the back cat.after i changed my o2 sensors it started bringing up a p0420 code.just wondering how the sensors can distinguish between bank 1 and bank 2 with only 3 sensors and if there is a specific sensor i need to get before i change the bank 1 cat.

  10. how about a 6 cylinder engine single exhaust with a bank 1 sensor 1 and bank 2 sensor 1, and then 1 O2 sensor after both manifolds come together but before the CAT? would that be a continuation of bank 1 (sensor 2)? along with the 4th O2 sensor after the CAT (bank 1 sensor 3?)

  11. Hello can you guys help me find bank 1 oxigen sensor on a chevy impala LT 2007 and where is it located i appreciate it

  12. Due to a very high demand and high ammount of comments, you have to wait for some time for your car questions to get answered. If you want to get fast answers from a certified master technician you can ask your questions here:
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