Mechanics

O2 SENSOR REPLACEMENT

2002 Chevrolet Malibu

How difficult is it to replace the inflow O2 sensor on a 2002 Chevy Malibu?
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Shade_tree_mech
December 13, 2010.




"inflow"? There is nothing identified that way. The 0/2 sensors all have a specific designation like B1S2, B2S1. Etc. Why are you changing it? Most codes referring to 0/2 sensors are not indicating a bad sensor.
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Wrenchtech
Dec 13, 2010.
Replacing the inflow sensor since that is what the computer identified as the reason for the check engine light coming on. It is the one that is on top, I believe that it was referred to as the B1S2?

Tiny
Shade_tree_mech
Dec 13, 2010.
First, computers don't tell you what the problem is. They give you the specific circumstances that it monitored and the tech needs to determine what caused it. 90% of the 0/2 sensors changed were misdiagnosed for another problem. The sensor is just a reporting device. B1S2 means Bank 1, sensor 2 which would be a downstream sensor on bank one. Changing it is just a matter of unplugging it and unthreading it from the exhaust pipe. The usual issues are just getting access to some of them.

Wrenchtech
Dec 13, 2010.
Ok. Thanks for the answer. What else may be the cause since the code(s) that the computer returned was interpreted by the automotive guys at O'Reillys to be, and this is their words, "the inflow O2 sensor". I have already replaced the throttle body, catalytic converter (which did need changing), the mass air flow sensor, and replaced both spark plugs and wires (about 4 months ago).

Tiny
Shade_tree_mech
Dec 13, 2010.
What was the exact code number?

Wrenchtech
Dec 13, 2010.
Don't currently have it with me, but I can get it and let you know either later this evening when I get home from work or first thing in the morning. (Not sure how long you will be available?)

Tiny
Shade_tree_mech
Dec 13, 2010.
I monitor this all day. Go ahead and get the code number.

Wrenchtech
Dec 13, 2010.
Ok got the full code. It comes up as PO 420 Catalyst System Efficiency. Hope that helps.

Tiny
Shade_tree_mech
Dec 13, 2010.
OK, that is not an 0/2 sensor problem. That is a catalyst efficiency code. 99% of the time, this is a bad catalytic converter. If you have already changed it and are still getting the code. Look for an exhaust leak ahead of the cat or you just used the wrong converter. Many of the aftermarket converters just don't do the job in place of OEM Cats. There is an outside chance of the 0/2 causing this but it's highly unlikely

Wrenchtech
Dec 13, 2010.
Thanks for the info. Will definitely investigate the leak as well as re-verify the catalytic converter since it was just put on about 6 months ago and is still under warranty.

Tiny
Shade_tree_mech
Dec 14, 2010.

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