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Oxygen Sensor Locations

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When troubleshooting oxygen sensor problems with a scan tool, you may find a diagnostic trouble code for one of the O2 sensors. The code displayed on your scan tool will indicate the type of fault, and identify one of the oxygen sensors by its position in the exhaust system.

The oxygen sensor's location will be identified by position (sensor 1, sensor 2 or sensor 3), and by cylinder bank (bank 1 or bank 2).

Most late model engines have multiple oxygen sensors, so which one is sensor 1, 2 or 3, and how do you know which cylinder bank is 1 or 2?

On straight four and six cylinder engines, there is only one bank of cylinders. So all of the oxygen sensors will be bank 1. The oxygen sensor or Air/Fuel sensor closest to the engine in the exhaust manifold will always be Sensor 1. The O2 sensor located in or behind the catalytic converter will be Sensor 2.

On V6 and V8 engines, Sensor 1 will always be on the SAME side as the Number ONE cylinder in the engine's firing order.

On Ford V6 and V8 engines, for example, cylinder number one is typically the RIGHT front cylinder on the passenger side in a rear-wheel drive car or truck.

On a Ford front-wheel drive car or minivan with a transverse (sideways) mounted engine, the number one cylinder is on the back side of the engine (closest to the firewall) on the right (passenger side) of the engine.

On GM and Chrysler V6 and V8 engines, cylinder number one is typically the LEFT front cylinder on the driver's side in a rear-wheel drive car or truck.

On a GM front-wheel drive car or minivan with a transverse (sideways) mounted engine, the number one cylinder is on the front side of the engine (closest to the radiator) on the right (passenger side) of the engine.

On a Chrysler front-wheel drive car or minivan with a transverse (sideways) mounted engine, the number one cylinder is on the back side of the engine (closest to the firewall) on the right (passenger side) of the engine (like a Ford).

To look up the firing orders for various engines, use the following links:
Firing Orders (Chevy)
Firing Orders (Chrysler)
Firing Orders (Ford)

The location of the number one cylinder on import engines will vary depending on the year/make/model.

One way to find number one cylinder so you can identify bank 1 is to look at the ignition system. If it has a distributorless ignition system (DIS) or a coil-on-plug (COP) ignition, the plug wires or coils may have lettering or marking indicating the cylinder numbers.

If a V6, V8 or V10 engine has dual exhausts with dual converters, the downstream O2 sensors would be labeled Bank 1, Sensor 2 and Bank 2, Sensor 2. Or, the downstream oxygen sensor might be labeled Bank 1 Sensor 3 if the engine has two upstream oxygen sensors in the exhaust manifold (some do to more accurately monitor emissions).

oxygen sensor locations

It's important to accurately identify which oxygen sensor is which so you can replace the correct sensor.
Oxygen sensors are expensive and difficult to replace, so you want to make sure you have the correct location before you replace anything.




Related Articles:

scan tool companion information Oxygen Sensors
Wide Ratio Air Fuel (WRAF) Sensors
Sensing Emission Problems (O2 Sensors)
Making Sense of Engine Sensors
Understanding Engine Management Systems
Powertrain control modules (PCMs)
All About Onboard Diagnostics II (OBD II)
Zeroing in on OBD II Diagnostics
Catalytic Converters
Troubleshooting a P0420 Catalyst Code

To More Technical Info Click Here to See More Carley Automotive Technical Articles

To Sensor Guide
Click Here to Get Sensor Guide


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