One of the very easy (but wild-sounding) things your portable code reader will ever relay to you is an issue to the effect that ‘bank 2 sensor 1’ needs attention.
Without an appreciation of where bank 2 of an engine is (and whether the second sensor on that bank is upstream or downstream), scratching of the head is likely to begin and frustration, at this point, is (also) likely to set in, especially if you’re faced with conflicting search results online.
Today, I’ll explain the concept of bank 2 sensor 1 as simply as I can. I believe, earnestly, that after today’s article, you’ll never forget either the bank or sensor position again, when it presents itself.
If you missed the first two installments, consider reading them here and here.
First things first though: where does the term, ‘bank 2 sensor 1’ apply in the first place?
Article Outline
Where Does the Term ‘Bank 2 Sensor 1’ Apply?
The term, bank 1 sensor 2 applies to a unique oxygen (O2) sensor on a particular and distinct engine bank. It spells, clearly, the position of the sensor and the bank that the sensor is on so that you know exactly what you’re dealing with or are up against.
In this case, it’s the second bank of an engine: the second bank is always the bank opposite the option housing cylinder number one.
To make it simpler, it’s the bank of the engine on the radiator side of the hood (on a transversely mounted engine). Transversely mounted engines are found on FWD systems such as the Corolla, Camry, Yaris, etc.
On longitudinally mounted engines (as found on 4WDs, RWDs, and AWDs) such as the Land Cruiser, G Wagen, Range Rover, W124 Mercedes, etc., this bank would be on the passenger side of the engine bay.
So, in summary, bank 2 sensor 1 simply points to the first sensor, before the catalytic converter, on the second bank of an engine as already explained above.
Having explained this, what does an oxygen sensor do?
What does an Oxygen Sensor Do?
It depends on the position of the O2 sensor in question: an oxygen sensor located before the catalytic converter on that bank is solely responsible for determining the air-fuel ratios happening on that bank.
Conversely, an oxygen sensor located after the catalytic converter is responsible for monitoring the oxygen levels, post-combustion, with a view of keeping vehicle emissions under control.
Differentiated on a bank by the designation ‘1’ and ‘2’, the first sensor handles the air-fuel mixtures while the second deals squarely with emissions control.
This is why more than one O2 sensor is needed, per bank of an engine.
Where Is O2 Sensor Bank 2 Sensor 1 Located?
By now, the position of the first sensor on the second bank of an engine should not be a challenge. However, if you’re still in the dark, the location of bank 2 sensor 1 is before the catalytic converter, on the second bank of the engine.
This, generally, is the sensor responsible for air-fuel mixtures. It is also worthy of note that, generally, i4s and many straight 6s don’t have ‘bank 2’ so technically, ‘bank 2 sensor 1’ doesn’t even apply to such engines in the first place.
The options you’re going to see with this configuration, to a large extent, remain the V6s and 8s.
Is Bank 2 Sensor 1 Upstream or Downstream?
Bank 2 sensor 1 is an upstream sensor, being that it is before the catalytic converter on that bank and deals mainly with air-fuel ratios and nothing else.
It’s ‘converse’, the sensor referred to as bank 2 sensor 2 is responsible for monitoring emissions from that bank, doesn’t deal with air-fuel ratios, and is rightly called, ‘downstream’.
Wrap Up
O2 sensors, their positions, and what they do are all key and central to understanding how an internal combustion engine works.
For you to be a good (and responsible) car owner, you’ll need to understand these little points, firsthand, to be able to handle the minor challenges that your vehicle faces and for the big ones, understand the technicians when they explain what’s wrong in ‘mechanicspeak’.
Who knows? One day, you’d also end up tearing engines apart and playing with transmissions!
This is an ongoing series. The next article is: Bank 2 sensor 2: upstream or downstream?