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2003 Ford Focus 1.6L 40000 miles: code P0420


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anand
New User

Oct 4, 2011, 4:38 AM

Post #1 of 8 (10512 views)
2003 Ford Focus 1.6L 40000 miles: code P0420 Sign In

Hi All,
Just 8 days back, my car's engine diagnostic light turned on while I was driving. The next day, using a friend's code-reader tool, I found that the problem it had was :
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
I erased it. I had booked Servicing and MOT test the same day so I took the car there, told them about the code and that I had erased it. The car passed the test without any problems.
Now, after 6 days, the light again turned on yesterday and I checked the code just now and its the same code i.e. P0420 and no other errors found.
Now, if my car passed the pollution test, just few days back, can this problem be genuine or is it just some sensor gone wrong.
What do you guys suggest I should do. Should I just
1) ignore it or
2) keep erasing it when'er the diagnostic light turns amber and ignore it
3) taking the car to some repair-shop?

Thanks


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 4, 2011, 5:38 AM

Post #2 of 8 (10484 views)
Re: 2003 Ford Focus 1.6L 40000 miles: code P0420 Sign In

You're going to need a new Catalytic Converter. It is failing the efficiency test.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



anand
New User

Oct 4, 2011, 5:42 AM

Post #3 of 8 (10480 views)
Re: 2003 Ford Focus 1.6L 40000 miles: code P0420 Sign In

Hi HammerTime,
Thanks for your inputs. But how come the car passed the MOT test? Also, generally, the need to change Cat doesn't arrive at so early stage of just 40k miles. Just asking in case your deduction is based on some other basis/logic which I might be missing.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 4, 2011, 6:17 AM

Post #4 of 8 (10474 views)
Re: 2003 Ford Focus 1.6L 40000 miles: code P0420 Sign In

Passing the MOT test doesn't mean anything because that was just a snapshot in time of all the emissions components working as one. There are some rare other causes but it's usually a bad cat because the criteria for setting the code is very specific and measured over a period of time.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



anand
New User

Oct 4, 2011, 7:21 AM

Post #5 of 8 (10468 views)
Re: 2003 Ford Focus 1.6L 40000 miles: code P0420 Sign In

Thanks again.
Actually, I then looked the at the two O2 sensors reading and they show quit difference readings which then indicates, if I am not wrong, that CAT is doing something. Isn't it.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 4, 2011, 7:54 AM

Post #6 of 8 (10463 views)
Re: 2003 Ford Focus 1.6L 40000 miles: code P0420 Sign In

That doesn't indicate anything. The reading are in constant fluctuation in milliseconds. If the computer sees the rear one mirroring the front one, it flags it.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Oct 4, 2011, 8:29 PM

Post #7 of 8 (10440 views)
Re: 2003 Ford Focus 1.6L 40000 miles: code P0420 Sign In

You might also want to see if there are any software updates for your PCM that may concern the P0420 code. Sometimes the on board diagnostics software values may be too sensitive when running the catalyst monitor causing a false positive. Might want to check for updates before condemning the converter.





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Blulakr
User

Oct 10, 2011, 10:14 PM

Post #8 of 8 (10393 views)
Re: 2003 Ford Focus 1.6L 40000 miles: code P0420 Sign In

+1 on checking for PCM reprograms before replacing cat convertor. Otherwise like previously stated 99% sure the convertor is going bad. You could just keep clearing the code but what if the light comes on for a different, more serious problem and you just assume it's another P0420.






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