Hi

I have a Ford Focus 2000 . Since 10 months ago my car has multiple occasions of engine light notices . When I checked them it was all oxygen sensors. So I change them twice but the engine light started to light on again after 2-3 weeks.

What should I do ?

 

Many times a code will direct you to the system and not always to the defective component. An understanding of how the system is supposed to function is necessary in order to determine what is working and what is not. Replacing parts and hoping for the best can get quite expensive these days. If you can get the present codes in the vehicle's computer, we may be able to shed some light on what might be happening.
Good practice requires finding the root cause before considering the problem corrected and it would seem in this case replacing the oxygen sensor(s) corrected the result , but not the cause. The better thing to do would be to get the present codes in the computer, then clear them , and see if they come back then those should be the latest problem codes. If they weren't cleared previously it could send one on a wild goose chase.

 

Hello

Thank you for your response. I checked the code , its 420.
I will be appreciated if you guide me.
Again thank you

 

Is that code PO420 ?
If so, From the info I presently have available, it says , "Catalyst System Efficiency " below limit - Bank No 1
This would concern the catalytic converter for the cyl 1,2,3 etc. I would suggest to have the system rechecked because converters are expensive and a second opinion is always a good idea when considerable expense is involved.