What Side is Bank 2 Sensor 1? (Location)

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Reduced fuel mileage, failed emissions tests, and a fault code like P0154 – savvy car owners know what these symptoms mean. But for the uninitiated, correctly identifying and locating the culprit can cause confusion and panic. Getting you acquainted with O2 sensors and helping you determine what side is Bank 2 Sensor 1 should help simplify things a bit.

Bank 2 Sensor 1 (a.k.a. B2S1) is located on the side of the engine with cylinder 2 in the firing order and the O2 sensor situated in front of the catalytic converter. Depending on the car’s make and driver orientation, it could be found on either the driver or passenger side of a vehicle.

Many vehicle owners feel intimidated by inaccessible vehicle components and intricate/complex engine layouts. But hopefully not anymore. With the help of this guide and the use of cylinder firing orders as a reference, you should find it easier to locate, diagnose, and repair B2S1 O2 sensors.

Oxygen Sensor O2 on Header Exhaust Pipe

“Where Do I Find My O2 Sensor?”

This query is nothing new for most (if not all) car owners. Since the implementation of ODB-II directives in 1981, anyone driving or repairing a car had to deal with O2 sensors. California initially pushed for these plug-like components to be mandatory in all vehicles driven within the state, following stricter emissions regulations.

The role of an O2 sensor is vital, as it helps ensure that your car’s fuel mixture is running neither too rich nor lean. When defective, it can adversely affect the engine’s timing and combustion efficiency (among other things). It is for these reasons that O2 sensors need to be kept in check and immediately repaired or replaced when needed.

Making Sense of Different Engine Configurations

Someone dealing with an illuminated Check Engine Light and a fault code may discover that locating O2 sensors is not that simple. How easily one can do this depends on their vehicles’ engine and cylinder arrangement.

Multi-cylinder engines (typical of modern-day automobiles), for instance, have three distinct arrangements – inline, V, and flat (horizontally opposed). Consequently, each of these engine types would have either one or two banks and different placements for O2 sensors.

So, What Side is Bank 2 Sensor 1?

Bank 2’s location varies in every automobile. It depends on its make and model and driver orientation (left-hand or right-hand drive). It would be presumptive to simply say it is found on the passenger side (although this is predominantly true for rear-wheel drive). By definition, Bank 2 refers to the side of an engine with the cylinder firing orders 2, 4, 6, 8, 10, and 12. It is the opposite of the B1S1 (Bank 1 Sensor 1) location.

Identifying the location of cylinder 2 pretty much tells you the location of Bank 2. But between rear-wheel and front-wheel drive automobiles, locating Bank 2 in the latter proves more difficult. Determining the “front side” of the engine – the position closest to the crankshaft pulley – is imperative. And while the “front side” is usually closer to the glass than the radiator, this layout is not guaranteed for all front-wheel-drive vehicles.

How to Find Bank 2

Here’s are some things to help you confirm the correct location of Bank 2:

1. Check for Stamps on the Cylinder Head or Block.

Some vehicles have stamps in their crankcase, which will help you confirm where cylinder 2 (and ultimately, where Bank 2) is.

2. Inspect if the Ignition Cables Are Numbered.

Depending on your vehicle type, your ignition cables may or may not have a mark on them. You are in luck if they do, although make sure that they have not been previously tampered with (typical of secondhand cars). Otherwise, you may have wrong information in determining which side is Bank 2.

3. Search up the Firing Order.

Other engines come with a sticker detailing their firing order. If your vehicle happens to have one, it will be easier for you to pinpoint where Bank 2 is. Otherwise, seek assistance from your local parts store or dealer to print out your engine’s firing order for you. Looking up the information in Google should be your last resort.

4. Use a High-Spec OBD-II or DRB-III Scanner.

This is the best (not to mention most iron-clad) step you can take to ensure you locate your car’s Bank 2 correctly. Using a diagnostic scanner like Launch X431 Pad V All-in-One Automotive Scan Tool (view on Amazon), unplug the wiring harness of the closest O2 sensor to the exhaust manifold on either side of your car’s power mill.

Next, turn the ignition key on. This will prompt your PCM/ECM/ECU to trigger a trouble code. The error will detail whether the unplugged O2 sensor is located on your engine’s Bank 1 or Bank 2.

5. Ask For Help From Someone More Experienced.

It could be a friend, a local mechanic, or an authorized dealer in your area. This is the least invasive way to make sure you locate Bank 2 Sensor 1 (or B2S1) the right way. Learning will be smoother (if you are a first-timer), but you will also prevent expensive repair expenses from replacing one too many O2 sensors.

Owners need to note that locating Bank 2 only applies to vehicles with at least a V6 power mill. Automobiles with four-cylinder and six-cylinder inline engines only have one bank. In case of an O2 sensor problem in these vehicles, one need only determine if the affected component is Sensor 1 (a.k.a. pre-cat, upstream sensor) or Sensor 2 (a.k.a. post-cat, rear, or downstream sensor).

Bank 2 Locations

Here is a list of Bank 2 locations in some of today’s widely-used vehicles:

VehicleBank 2 Sensor 1 Location
Chevrolet ColoradoPassenger side with cylinder 2 in the firing order, in front of the catalytic converter
Ford BroncoOn the exhaust end, before the catalytic converter
Ford RangerDriver side, before the catalytic converter
GMC SierraPassenger side, before catalytic converter
Honda CivicAccessible under the hood before the catalytic converter
Hyundai TucsonRadiator side of the engine, before the catalytic converter
Kia StonicSide with cylinder 2 in the firing order, on or right after the exhaust manifold
Land Rover DefenderLeft-hand side, before the catalytic converter
Nissan Patrolunder the flange for the y-pipe, in the exhaust manifold closest to the radiator
Subaru OutbackUnderneath the hood or the vehicle, sensors are screwed to the exhaust pipe in front of the catalytic converter
Suzuki XL7driver side, above the catalytic converter
Toyota RAV4Passenger side, on the exhaust manifold or catalytic converter (accessible under the car’s heat shield)
Volkswagen TiguanPassenger side, in front of the catalytic converter

Bank 2 Sensor 1 (B2S1) Trouble Codes

Although issues with O2 sensors do not occur as often as other vehicle faults, knowing how to locate and access them is crucial. You may have no urgent need for a sensor replacement (especially if your vehicle has under 100,000 miles). Visit obd-codes.com for a complete list of sensor-related fault codes.

A tip for Mercedes-Benz owners: Pre-1996 Mercedes-Benz vehicles had a biodegradable engine harness, increasing the likelihood of poor grounding and O2 fault codes. Daimler AG resolved this issue for ’96 models onward with the updated Bosch engine management (coil-pack setup). If you have a pre-’96 model, make sure to first check on the integrity of the harness before deciding to replace suspected O2 sensors.

Conclusion – What Side is Bank 2 Sensor 1?

The most fool-proof way to locate Bank 2 Sensor 1 is by determining where cylinder 2 is. You can refer to the engine diagram or the cylinder firing order in your service manual. Using a high-spec OBD-II or DRB-III diagnostic tool would be the next best step – although this method may prove tedious since it is somewhat hit-and-miss in nature.

Vehicle-specific online forums also provide great input on dealing with seemingly inaccessible components and persistent O2 errors. And if all else fails, do not shy away from consulting a professional mechanic or your local auto shop.

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