Im changing O2 sensors on 2004 Ford Expedition and noticed upstream and downstream sensors look different. I bought four O2 sensors from Autozone and they all look like the downstream sensor. Can I use these as upstream sensors?. Is this ok

The 2005 Jeep Grand Cherokee Laredo 3.7L typically has two oxygen (O2) sensors. One is located upstream (before the catalytic converter), often referred to as the pre-cat or upstream sensor, and the other is located downstream (after the catalytic converter), known as the post-cat or downstream sensor. In many cases, the upstream and downstream sensors are not the same and serve different purposes in monitoring and optimizing the air-fuel mixture and emissions.

Question edited for clarity and spelling of 'Expedition'.
Question moved from Misc to model category.

Yes, depending if they are upstream or downstream, they can be hard to reach and really need to be up on a lift at a garage.

Videos that might help, but it is a fast job for a pro tech and you need a special wrench.

https://www.google.com/search?q=2001+Ford+Expedition.+How+to+change+the+o2+sensor

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There should be just 2 02 sensors on your car an upstream and a downstream

Here is the link for both the upstream and downstream 02 sensor

Amazon com B072WPRVF6

The upstream O2 sensors are just off the engine exhaust manifolds, the downstream sensor is located aft of the catalytic converter, it is not called an O2 sensor it is referred to as the catalyst efficiency monitor.

Hi Jesus, Im AL the owner of Big As Auto Repair.

If you have a 4 cylinder engine then you will only have two 02 sensors 1/1 is upstream and 1/2 is downstream. Upstream is the one closet to the engine and downstream is the one farther away from the engine.

If you have a six OR eight cylinder engine you will have four 02 Sensors. 1/1 means Bank One Sensor One. 1/1 and Bank one means right bank and right bank means the side with the number 1 spark plug. SO, 1/1 means, "Right Bank" Upstream 02 sensor. 1/2 means, "Right Bank" Downstream 02 sensor.

2/1 means, "Left Bank" Upstream 02 sensor and 2/2 means, "Left Bank" Downstream 02 sensor. Hope this helps and please visit my auto-repair-website at: http://www.bigasautorepair.com/

On a ford all the sensors have a wire that heats them you have upstream sensors up by the engine and downstream sensors located on or before the converter.

http://www.bbbind.com/technical.html
Free wiring diagrams & TSB's-all makes and models. Your 4 O2 sensors are shown under System: engine, Subsystem: fuel controls.

First what do you mean by a universal o2 sensor? You must make sure that you have the right o2 sensor, most newer vehicles have four o2 sensors 2 upstream and 2 downstream, upstream and downstream are meant to show where the sensors are in relation to the catalatic converter,some o2 sensors have 1 wire or up to 4 wires most with four wires are heated o2 sensors so you need to be sure you ve gotten the right o2 sensor for you vehicle as well as the right replacement for the proper location! My experience is that most after market o2 sensors have the same colored wires as the vehicle. Also most o2 sensors have electrical plugs? If you need help finding the right o2 sensor for your vehicle then please dont be affraid to ask!

Your auto has four O2 sensors. Two upstream and two downstream; With two banks. Bank 1, sensor 1...and bank 2, sensor 1 are the two upstream (exhaust manifold before the catalytic). Bank 1, sensor 2 and bank 2, sensor 2 (other side of catalytic)

Code 1131= upstream; bank 1..sensor 1
Code 1151= upstream; bank 2..sensor 1
Code P0136 (generic code) bank 1..sensor 2 (questionable)

I wouldn't spend the money to purchase 3 sensors. Highly unlikely all three are bad; Cost is about $40/ ea.
Since there isn't a code for the cat's themselves, I would suspect the O2 circuit is malfunctioning. The rough idle is another clue.


Take an ohmmeter set it on X10 scale and measure the resistance from engine to body and body to negative post on battery terminal. You should read zero ohms (full needle deflection). If you do go buy two upstream O2 sensors. If you read
open or a high resistance run two straps from eng. to body...and body to neg.batt. post.

FixYaWIZ................saailer



I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

On four cylinder models, the upstream oxygen sensor is located at the upper end of the catalyst pipe, right below the exhaust manifold flange (the downstream is located on the catalytic converter itself).
On four cylinder models, the electrical connector for the upstream oxygen sensor (the one before the catalytic converter) is behind the cylinder head, just to the left of the rear engine mount bracket (or you could find the sensor and simply follow the wire). Depress the release tab and and disconnect it.
Raise the vehicle.
Unscrew the sensor (since it has a wire coming from it, and a shield around the place where it goes in, you would be advised to rent a sensor removal wrench from Autozone or one of the same sort).
Autozone also carries the sensors. They are pretty expensive, something like $60.00, I think.
Hope this is helpful to you.