Contour Enthusiasts Group Archives Forums General Troubleshooting Oxygen Sensor Replacement

Car Info 1996 SE V6 2.5L 110K Miles.

I'm going to change my O2 Sensors this weekend when the weather gets better so I am trying to find out more information about replacing them.

Anyway, my question is that from reading through the threads, I understand there are 4 oxygen sensors. Of which I located the first oxygen sensor Upstream Bank 1 O2 Sensor Replacement

My question is where are the other 3? Can someone illustrate the locations to me?

Other question is I went to autozone and the codes I pulled are P1131, and P1151. The guy told me my car only has 2x O2 sensors therefore only sold me 2. Should I go back and buy another 2? or just replace 2 of them?

The downstream sensors long outlast their rated life (only thing on the car).

The upstream sensors are on the exhaust manifolds. One in front (bank 2), one in back (bank 1). The one in front is under the plastic cover.

My downstream failed at 57000 they dont last very long.

okay, so for my code P1131 and P1151 should I replace the upstream sensors with the Bosch 13115 on bank 1 and bank 2? Does anyone know the return policy of Advance Auto? I probably need to change the Downstream Sensor for the UpStream to make a set of two upstreams.

Someone please confirm with me. Thanks!!

P1131 and P1151 are lean codes for banks 1 & 2.

This can be the upstream sensors going out (over about 80k miles) since the upstream sensors control fuel trim.

These codes can also be caused by low fuel pressure, dirty MAF, vacuum leaks...

At 110k miles, I would go ahead and replace the upstreams if they are original.

There should be no reason to replace the downstream sensors. They only alert the computer if they sense CAT problems. They do not affect engine operation and rarely go bad because they stay clean behind the CATs.

Most places will accept full return if merchandise is unused.

If these 1131/1151 codes are concurrent, I would look to other things before changing both of these sensors. Changing these out is not easy work. At 110k, sure it is not a bad idea to change them but it may be something else that is causing them to trip the CEL.

If you have located bank 1, sensor 1, bank 2 sensor 1 is in the same location on the opposite bank .... ie somewhere below the top of the rad. Sensor 2 on both banks can be found at the bottom of the respective precats. They are easily seen while under the car.

MarkO,

since it can be seen easily under the car, would you recommend me to change the sensor from underneath or still from the top?

I do have access to a car lift but I do need to ask the permission of the owner if working from below is the easiest.

Btw, I went by Advanced Auto and they looked at me strange when I told them I needed to replace the downstream for a second bosch upstream sensor. He told me in his life he has never seen a car needing two identical upstream sensors.

I meant to address this to anyone else too if they can help me instead of just MarkO.

Thanks

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since it can be seen easily under the car, would you recommend me to change the sensor from underneath or still from the top?

I do have access to a car lift but I do need to ask the permission of the owner if working from below is the easiest.

Btw, I went by Advanced Auto and they looked at me strange when I told them I needed to replace the downstream for a second bosch upstream sensor. He told me in his life he has never seen a car needing two identical upstream sensors.

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I replaced the bank 1 sensor from the top. You may want to remove the plugs from the coil pack and a wiring harness in order to get a decent space to manuever your arm. Also, perhaps some liquid wrench if the sensors are TIGHT.