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George H.
George H. , ASE Certified Technician
Category: Mercury
Satisfied Customers: 18216
Experience:  ASE Master 15+ years
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2000 Mercury Cougar: Evening,The check engine light..o2 sensor

Customer Question


The check engine light on my 2000 Mercury Cougar came on and the parts place says it's either the O2 sensor or the catalytic converter. I'd like to go ahead and change the sensor but there are 2 to chose from. Which one would you recommend I start with? Thanks
Submitted: 6 years ago.
Category: Mercury
Expert:  George H. replied 6 years ago.

Hello I will help you with your question,


If the code was a P0420 or a P0430 it is the cat that needs to be replaced but it is the rear O2 sensor that monitors the operation of the cat so if you are going to replace a sensor it would be the rear one.


Now the problem is which rear sensor to replace. There are left and right sensors on your V6 engine so I would need the code that was retreived from the computer to see which side is the issue.


Let me know what the code was and I can tell you which side to replace





Customer: replied 6 years ago.

How hard is it to work a code puller and is there a cheap one that you can recommend we get? It's for my son and I'm trying to get him into working on his car and would like to get him the code gadget if he needs one. The dealer wants to charge $70 but if he can get a code puller for that I'd like to go that route.



Expert:  George H. replied 6 years ago.

You can get an inexpensive code reader at most autoparts stores for $39.95 or they will read the codes at no cost. The Innova brand seems to be widely available and it is easy to use but limited in its abilities.




With the code we can track down what the computer is objecting to.


Let me know what I can do to help you with this







Customer: replied 6 years ago.

So which code goes to which sensor?

Expert:  George H. replied 6 years ago.

The P0420 is the cylinder bank with the number 1 cylinder making it Bank 1 and P0430 is Bank 2.


You have the setup on the left so the two #2 sensors are the rear catalyst monitoring sensors.



George H., ASE Certified Technician
Category: Mercury
Satisfied Customers: 18216
Experience: ASE Master 15+ years
George H. and other Mercury Specialists are ready to help you
Customer: replied 6 years ago.

We'll give it a try.


Thanks for your help,



Expert:  George H. replied 6 years ago.

Glad to help and please let me know if there is anything else I can do for you


Thanks for using JA!!



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