02 sensor

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

In Troubleshooting by Magnus Sellén30 Comments

Are you struggling to find out which O2 sensor you 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 once you have learned it once, it’s not that complicated.

I often hear about people who 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!

Bank & Sensor Shortcut

Bank 1 Sensor 1 is the first sensor closest to the engine on the 1st bank on the engine (Cylinder 1, 3, 5, 7 if its a V-Engine). Usually the left side of the engine from a driver perspective.

Bank 1 Sensor 2 is the second sensor on the exhaust pipe from the engine, usually behind the catalytic converter. Fitted on bank 1 which means the cylinder 1, 3, 5, 7, etc if it’s a V-Engine. Usually the left side of the engine from a driver perspective

Bank 2 Sensor 1 is the first sensor closest to the engine on the 2nd bank on the engine (Cylinder 2, 4, 6, 8 if its a V-Engine) Usually the right side of the engine from a driver perspective.

Bank 2 Sensor 2 is the second sensor on the exhaust pipe from the engine, usually behind the catalytic converter. Fitted on Bank 2 which means the cylinder 2, 4, 6, 8 etc if it’s a V-engine. Usually the right side of the engine from a driver perspective.

bank 1 vs bank 2

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 on.

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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 learn 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 is number 1, it 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 they 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 various 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.

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The most secure way is either to see if you can find it on the crankcase cover or find it on 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 the 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
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If you still have any questions about this, comment 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 it if you also checked out our other articles.

30 thoughts on “ Bank 1 vs Bank 2 – Sensor 1 & 2 – O2 Sensor Location ”

    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. Are sensor 1 the same on either bank in a vz commodore.
      Just asking as i have bank 2 sensor 1 fault in my car and i have another car with a near new sensor in bank 1 sensor 1 that is a parts car

  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. Brilliant overview Magnus! My OBD gives P229F & P2201 codes which seems to be NOx sensors but nothing else. How to find out which one is causing problem?

  13. Sorry, should have added; Merc CLS V6 so I’m assuming 4x sensors total, B1S1, B2S1, B1S2 & B2S2.

  14. You are wrong on Your V8 and V6 cylinder numbering. You’re correct that the front cylinder is # 1, but there are 2 connecting rods on each V type crank journal. GM and others place the drivers side rod in front of the passenger side rod making the drivers side cylinder about 1 inch in front of the passenger side as you show and the cylinders are numbered front to back just as an in line engine is numbered. Ford who had a V8 I believe in 1932 places the connecting rod on the passenger side in front making the front passenger side cylinder number one, and they continue with number 2,3,and 4 on the right side, and with 5,6,7,and 8 on the left. Different strokes for different folks, but we gotta follow the engineer’s lead.
    I have put a bank 1 position 1 oxygen sensor on bank 2 sensor 1 and another of the same one on bank 1 sensor 1 in my 1998 ford Explorer 5.0 with 329 K on it. I read that the bank 1 sensor would try to adjust the fuel on bank one no matter where it is installed mine runs good but I am going to replace it with the correct part. Can the bank 1 position i sensor be used in bank one position 2 safely.

  15. Thanks to this information. I am asking how to test o2 sensor with multimeter thanks again…

  16. I’m getting code p0449 and code p0420 on a Chevy suburban 5.3 what’s the best way to trouble shoot the problem and the traction control light keep coming on last time this happened I replaced spark plugs and was fixed months passed came back so I replaced spark plugs and wires but still running ruff…. please help point me in the right direction if possible thanks and God bless

  17. I have a 2007 Sienna Van. The check engine light stays on. Motor is a 3.5. Error codes given by Auto store is P0300, P0137 and P2196. Can you tell me what sensor parts I need to purchase to correct the engine light?
    Thank you

  18. So would the upstream o2 sensors on at 2003 Ford thunderbird be under the car on the exhaust manifold is it easy to get to? Without a lift.

  19. Hi I have a 2007 holden commodore 3.6l omega and I need to change my o2 sensor bank1 are you able to help me locate which side it is on ppl ease

  20. I own a 2008 Jaguar XJR in the US and am getting a P0430 code which points to “catalyst system efficiency below threshold bank 2”. I saw somewhere that the bank 2 is on the drivers side but need confirmation before I go ahead and replace it. Is there a diagram for 8 cylinder positions. My understanding is that odd number cylinders are on the passenger side and even numbers on the drivers side which makes the Bank 2 pointing towards drivers side. Please confirm if my understanding is correct.

  21. Could you hep find where is the camshaft sensor position for my toyota land cruiser prado 2012 diesel.
    i thank you in advance

  22. Due to very high demand and a high amount of comments, you might have trouble getting your comment answered by me. If you want to get fast answers from a certified automotive technician you should ask your questions here: Ask A Mechanic

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