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P0420 OBD-II Trouble Code..great

acontour

CEG'er
Joined
Dec 14, 2007
Messages
245
More and more problems. Even though the car seems to run fine I keep getting the P0420 code(Catalyst System Efficiency Below Threshold (Bank 1)

It's a brand new high flow exhaust system with : high flow cat , 2.5" pipes,magnaflow muffler and both O2 sensors new.. Is it just my Computer going crazy ?? Has anyone else experienced this trouble code?

Thanks
 
does your exhaust system include headers? if so thats the reason for the code.

If not your precat might be clogged. If so best solution is gutting the precats/buying headers and adding mil-eliminators. (which will eliminate the code)
 
Common fault code. SEARCH for it using the fault code as your SEARCH keyword. Very much discussed.

FWIW, it's not the O2 sensors, it's the lack of catalyst action.

MIL eliminators are most likely your best bet.

Steve
 
FWIW, it's not the O2 sensors, it's the lack of catalyst action.

I could be in one case. did you get any O2 sensor codes when you pulled the P0420 code? If so a bad sensor could cause the P0420.

if you want to confirm this swap the down stream sensors and you should get a P0430, if not then its really a P0420.

your best bet is mil - eliminators
 
does your exhaust system include headers? if so thats the reason for the code.

If not your precat might be clogged. If so best solution is gutting the precats/buying headers and adding mil-eliminators. (which will eliminate the code)

Yeah , I also added the SVT long tube headers.The catalys is a high flow one , that I just recently had put on with the full exhaust system.. Where can I find that mil-eliminator?
Thanks
 
I could be in one case. did you get any O2 sensor codes when you pulled the P0420 code? If so a bad sensor could cause the P0420.

if you want to confirm this swap the down stream sensors and you should get a P0430, if not then its really a P0420.

your best bet is mil - eliminators

Yeah I'll most likely try the mil-eliminator because I changed both O2 sensors about a week ago.
Thanks for the help
 
I could be in one case. did you get any O2 sensor codes when you pulled the P0420 code? If so a bad sensor could cause the P0420.

if you want to confirm this swap the down stream sensors and you should get a P0430, if not then its really a P0420.

your best bet is mil - eliminators

Your system should have four sensors, not two. The MIL eliminators go on the downstreams.

You're missing something.

Steve

You guys need to look at his sig. he has a ZETEC so he only has one rear O2 sensor.


acontour said:
Yeah , I also added the SVT long tube headers

I want to see pics of how you installed the FSVT long tube headers on a contour. the pass under the oil pan for the exhaust is in the wrong spot to use focus headers.
 
You guys need to look at his sig. he has a ZETEC so he only has one rear O2 sensor.




I want to see pics of how you installed the FSVT long tube headers on a contour. the pass under the oil pan for the exhaust is in the wrong spot to use focus headers.

Yeah I know , after I got them I had a lot of issues but I had them moddified. The headers we're cut from the middle section . I will get some pictures some time this week.
 
Light went off

Light went off

In case you guys we're wondering , I drove the car for a little bit and the light went off. But it lacks power now (kind of like if the cat was clogged). Nothing seems to work right with this car.. It's a FORD
 
Nothing seems to work right with this car.. It's a FORD


:nonono: :nonono:

don't blame the car if it wasn't taken care correctly ....

I got my 95 with 86k and it now has 196k with little issue or problem, I have gotten more then my moneys worth out of that car and its still kicking
 
What wire for MIL Eliminator - Which Bank is which?

What wire for MIL Eliminator - Which Bank is which?

My car has the same issue - the PO420 Bank 1 code. I installed a MIL eliminator this weekend, turned the "Check Engine" light off and drove it for a few days to make sure the light stayed off. It came back on last night -

I installed the MIL eliminator to the black wire on the rear O2 sensor for what I thought was bank 1 of the V6- the back or RH side closest to the firewall. Is this Bank 1?

Did I install it on the correct wire? The directions said Fords get it installed on the black wire except for Mustang GT that have it on the gray. There is a
gray wire also. Anyone have experience with the MIL eliminators?

Help please!! I can't renew my tags until it passes the emission test - which is essentially no engine codes related to emissions.
 
jagman4,

Post the exact new CEL code.

Then look at the mileliminator installation instructions. The O2 sensor you want mess with is the one closest to the muffler, i.e., this is the one below the rear exhaust manifold (below the firewall). And it should the one closest to the ground (not electrical ground but God's green earth).

http://www.contour.org/ceg-vb/showthread.php?t=760
 
Same code after MIL Eliminator - PO420

Same code after MIL Eliminator - PO420

The code is the same PO420 - and I installed it as you suggested on the lower back O2 sensor. I spliced teh MIL eliminator into the harness for the back sensor and three days later the same code reappeared. Maybe I have a bad MIL Eliminator - I did not get it from the site suggested in the thread.

Also - mine only connected one wire - the black- not two as suggested by this post. Any help woul dbe great.
 
The code is the same PO420 - and I installed it as you suggested on the lower back O2 sensor. I spliced teh MIL eliminator into the harness for the back sensor and three days later the same code reappeared. Maybe I have a bad MIL Eliminator - I did not get it from the site suggested in the thread.

Also - mine only connected one wire - the black- not two as suggested by this post. Any help woul dbe great.

Yes, your mileliminator is the problem. Follow the instructions on the how to and you should be good.
 
Here's my question: If there's an issue with exhaust flow through the precat, and you simply install a mil-eliminator, how is that a thorough solution? Seems to me it's the precat that should be getting the attention.

If there are no issues with performance, could there really be a problem with the precat itself? Changing out the downstream O2 sensors won't solve the problem, I take it?
 
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