If you’re having trouble knowing which O2 sensor to replace, as a new driver, you’re not alone. Knowing which O2 sensor is Bank 1 and which is Bank 2 can be difficult but by the end of this, not knowing which O2 sensor corresponds to which bank will become old news to you. If you’re here, chances are that you’ve replaced the wrong sensor because you were unaware of the sensors bank. Luckily, you can take them out of the wrong bank after finding out the correct bank and install them there.
The term bank is used by manufacturers to identify one side of an engine. If you’ve had a problem which your O2 sensor and this was on the left side, some manufacturers refer to the left side would be O2 sensor Bank 1. Since some manufacturers assign Bank 1 to the left side or the right side, knowing which one it is can be difficult.
What is Bank 1 Vs Bank 2
Your engine cylinders are split into 2 parts which is why there are two different banks. Depending on which type of engine you have, you should have a bank on either side. On all v engines, this is the case. The problem with knowing which bank is on which side is that manufacturers don’t stick to one rule.
Either bank 1 or bank 1 can appear on either side of the engine cylinders or at the front or rear. There’s a misconception that bank 1 resides on the driver’s side but this simply isn’t true – this notion can’t be factored once you realize that some cars are left drive and some cars are right drive.
Where is Bank 1 and Bank 2?
Bank 1 is located on the side of the engine cylinders numbered 1 – 3 – 5 – 7. Bank 2 is located on the side of the engine numbers 2 – 4 – 6 – 8. It’s hard to specify where bank 1 and 2 are because it’s different depending on the engine you have. Bank 2 can be found on both transverse engines and inline engines. If you know which cylinder on your engine is numbered 1, you don’t need to worry about which engine you have.
Bank 1 is always located on the cylinder 1 – 3 – 5 – 7 – 11 and bank 2 is always located on cylinder 2 – 4 – 6 – 8 – 10 – 12. On an inline cylinder construction, the cylinder numbering starts (so number 1) from the side of the engine that has the serpentine belt and the last cylinder is the one closest to the flywheel. Number 2 will always be towards the person viewing from the belt side.
If you’re not sure which engine you have, you can locate the VIN number on your car. This is usually on the lower corner of the windshield on the driver’s side. You may be able to find it on the door frame on the driver’s side. Once you’ve got it, write down the VIN number and make sure to check it for errors. Go to decodethis and enter your VIN. Press decode and you may be asked to select the vehicle that closely matches your own then click ‘Select Trim’. On this page, you’ll be able to see your engine’s model, and trim and style. Chances are you’ll have a V-engine.
Which O2 sensor is 1 and 2
If you’re wondering which sensor is located where, there’s a rule to follow. The sensor number tells you where on the exhaust system the O2 sensor or Exhaust temperature sensor is located. The first sensor is located closest to the engine and the second sensor is located at the back of the exhaust system. Sensor 1 is usually before the Catalytic converter and sensor 2 is usually after the catalytic converter.
How to Find the Cylinder Number
There are a few ways that you can find the cylinders number. The is the hardest part about knowing where bank 1 and bank 2 are located is that you won’t know which side of the engine cylinder 1 is located. Once you know this, you’ll be able to identify quickly where bank 1 and bank 2 are located. Depending on the car you have, you might find the cylinder number stamped on the crankcase cover. If you have ignition cables, you may also find the cylinder numbers here.
The best way to tell which side Bank 1 and which side Bank 2 is to look at your car’s service manual. Your car’s service manual is there to help you when your car needs to be serviced and, in this case, you need help know which side your O2 sensors are located. Your service manual will let you know which side of the engine cylinder 1 is located, and from here, you’ll know that this side of the engine is bank 1. The start of the bank is always located towards the front of the engine.
If you have an OBD2 scanner, you can use this to find out where Bank 1 and Bank 1 are located. A professional OBD2 scanner tool (View on Amazon) will allow you to look up the location of both your sensors, whilst a standard OBD2 scanner tool may not allow you to do this. Once you have your OBD2 scanner, you can connect it to the connector underneath your steering wheel and press the red button on the scanner. From here, you need to wipe any error codes that the scanner gives you. Unplug one O2 sensor and check the diagnostic trouble code the scanner gives you. This will let you know whether Bank 1 or Bank 2s O2 sensor was unplugged. If you were doing this and you received code P0420 on the scanner, then it looks like you’ve got yourself a faulty O2 sensor and you’ll need to get it look out.
Another way to find out where your cylinders are located is by going to a workshop and having a mechanic tell you where they are. If you weren’t able to find the stickers or check your repair manual for the cylinder numbers, asking your mechanic would be the next best option. If this isn’t possible for you, you can try and search up your firing order along with your cylinder order.
Oxygen Sensor Locations Depending on Your Engine
Depending on which engine you have, you can find out where the Banks are located. If you’re not sure which engine you have, you can search it up the VIN code and decode it.
Traditional V6 and V8
On a V6 or V8 engine, Bank 2 is located on the left side of the vehicle and this is where sensor 1 goes. This is before the catalytic converter and it’s near the manifold. On the right side of the vehicle, this is where Bank 2 is located and it’s where O2 sensor 1 goes. This is also before the Catalytic converter. After the catalytic converter, Bank 2 is housed on the left and sensor 2 goes here. and on the right before the cat converter, Bank 2 is housed and sensor 2 goes here.
V6 and V8 Transverse
Before the cat converter, Bank 2 is located on the front and this is where O2 sensor 1 goes. Before the catalytic converter at the rear, this is where Bank 1 is housed and it’s where sensor 1 goes. After the cat converter you’ll find Bank 1 and this is where sensor 2 goes.
4 and 6 Cylinder In-line
Before the cat converter on the front of the vehicle you’ll find Bank 1 here and this is where Sensor 1 goes. Before the catalytic converter on the rear of the vehicle, you’ll find Bank 2, and this is where sensor 1 goes. After the cat converter, you’ll find Bank 1 and this is where sensor 2 goes.
4 Cylinder Transverse
On the front of the vehicle before the catalytic converter, you’ll find bank 1 and the is where sensor 1 goes. On the rear of the vehicle after the catalytic converter, you’ll find bank 1 and this is where sensor 2 goes.
How to Fix a Bad O2 Sensor
The O2 sensors help to gauge how much air and fuel is needed for the next combustion cycle. If the O2 sensor are damaged, then the engine could create the wrong air fuel mixture. If this continue, the engine will lose performance and it can eventually blow which is expensive to repair. Failing to maintain your O2 sensors and the engine over a period of time can cause can lead to a blown engine. Maintain parts of your car will ensure that you don’t have problems so if you’re experiencing them, it’s a sign that you’re about to spend a lot of money at the dealership.
If you want to avoid O2 sensor problems or other issues and save $100s of dollars that you’ll spend at the auto repair shop, you’ll need to service your vehicle often – you can use our mechanic-rated Auto Maintenance and Repair Manual to do this. It’s basically what mechanics use to go through your vehicle to check if there are any problems that need fixing. As soon as they notice the most minor problem, they’ll ask you to fork out some money even though it’s a problem you can fix yourself in minutes – the manual will teach you how to maintain your vehicle every few thousand miles and it’ll teach you how to fix minor problems that mechanics will ask you to pay for; saving you money in the long run.
A lot of our readers have the Auto Maintenance and Repair Manual printed on their garage wall and 92% of them haven’t visited the auto repair shop in the last year because they know what to do to avoid problems. All it takes is giving your vehicle a little attention every few thousand miles and you’ll never spend money at the workshop again.
What to Do if you Replaced the Wrong Sensor
If you or your mechanic has mistakenly located Bank 1 and Bank 2 on the wrong sides and installed an O2 sensor on the wrong bank, this can cause the same symptoms as a faulty O2 sensor. If you’ve realized that the O2 sensor has been installed in the wrong Bank, you’ll notice the following symptoms:
Check Engine Light – When the check engine light comes on, it means that your engine control unit is having an issue regulating or maintaining a problem within the vehicle. The O2 sensor is important for the fuel and air mixture. If the sensor thinks that there’s less oxygen in the exhaust gases after combustion in the combustion chamber and the sensors aren’t working properly to determine the correct levels of oxygen, the engine control unit won’t be able to regulate it, therefore, the check engine light will come on.
Bad Fuel Economy – if the intake manifold has created a rich air-fuel mixture in the engine due to your o2 sensor being installed incorrectly and there’s more fuel than air, it can cause more fuel to be burned in the combustion chamber and this can result in a bad fuel economy.
Weak Engine Performance – since the combustion process of your car isn’t normal, you’re going to be presented with a bad engine performance. You’ll notice this when you’re driving because as soon as you accelerate, you’ll notice that the engine isn’t as powerful as it used to be.
If you notice any of these symptoms, chances are that the O2 sensors where installed in the wrong bank and has caused you problems that never existed in the first place. If this is the situation, you’re in, you’ll need to get the O2 sensor out of the Bank that it’s incorrectly installed in and install it in the correct Bank. You need to be sure that the O2 sensor you’re installing isn’t faulty itself and the sensor you’re taking out of the incorrect bank is working properly.
Replacing O2 Sensor
If you have faulty O2 sensors in the first place and you needed to identify where Bank 1 and Bank 2 are to make sure that the sensors are installed in the correct bank, then it’s time to get it replaced. If you’ve looked at the symptoms of a bad O2 sensor above and you’ve concluded that they need replacing, then you’re looking at thousands of dollars. It’s best to get O2 sensors replaced by yourself because you won’t be paying for labor costs and mark-up costs.
Depending on the model of your vehicle, the average O2 sensor will cost your $200 to $400. The O2 sensor itself cost about $130 to $250 and the labor cost around $100 to $150 depending on the workshop or mechanic you go to. If you do decide to replace the O2 sensor yourself, its not difficult and now that you know which Bank it’s meant to go on, you should have no issues.