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2002 fire bird replaced the cat converter all three sensors still getting p420 code

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Are you sure that the rest of the exhaust system is not blocked (muffler)
No leaks before converter
No engine misfires
Thermostat works
Temp Sensor okey
Check other non displaced ECM Codes stored
No air pockets in cooling system

Posted on May 13, 2010


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1 Answer

2006 Subaru Forester with a P420 code. Can this be fixed by replacing a universal converter?

Unfortunately, universal catalytic converters do not have enough oxygen storage available and the code will return quickly if you use them. Asian imports are very touchy about this, Subaru's and Toyota's hate aftermarket universal cats!

Mar 03, 2015 | 2006 Subaru Forester

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Check Engine Light. I have p420 P440 and P446 codes

You need a Catalytic converter and possibly a Evap. cannister

Oct 04, 2014 | 2003 Toyota Corolla

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What does trouble code p0420

p420 code has to do with your exhaust system,catylic converters,..sensors...could be a simple fix or not...

Sep 19, 2014 | 2003 Chrysler Town & Country

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Innova 3100 codes manual

replace your rear oxygen sensor ,,,if that does not clear your code after about a 100 miles than you need a cat converter ,,if you have a bundle of miles on it already that will most likely be your issue

Aug 25, 2014 | Cars & Trucks

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Suzuki Grand Vitara 2007 - Efficiency low on bank 1 engine light. is it just the sensor or do i need a new cat? is this common?

Is the code P420 ? Is there an exhaust leak in front of cat? If not you need a new cat. Recommend one from Suzuki. cheap ones don't last more than a year or so. If it was a sensor you would have a different code. Can only be bad cat or exhaust leak before cat allowing fresh air to be pulled in.

Dec 05, 2013 | 2002 Suzuki XL-7

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P420 code

P0420 means the cat converters tests below minimum efficiency. That can be caused by an exhaust leak. Take it to a small independently owned (NOT A CHAIN PLACE) shop to get a quote.

Sep 02, 2017 | 2002 Dodge Grand Caravan

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2002 mitsubishi lancer oz rally troubleshooting p0420

Code p0420 is 'catalyst efficiency below threshold'.

This could be caused by a bad catalytic converter but before dumping a ton of money on that I would suspect the after-cat oxygen sensor is getting lazy and setting the code.

Have the O2 sensors checked and replace if needed before suspecting the catalytic converter.

Good luck.

Feb 11, 2010 | 2002 Mitsubishi Lancer

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I have an engine light on to my Toyota Corolla 2003; diagnosed by the autozone OBD11 SCANNER P420. I replaced the oxygen sensor and the light deleted. After driving the car for 30 miles the light came on...


The trouble areas associated with this code are as follows:
1)Gas leakage on exhaust system
2)Oxygen sensor
3)Heated oxygen sensor
4)Three–way catalytic converter

The idea is to check for exhaust leaks first then the front sensor and rear sensor. If these all check out then the cat needs to be replaced.

Hope this helps. Thanks for using fixYa

Nov 05, 2009 | 2003 Toyota Corolla

1 Answer

I keep getting this p420 code of and on , also when my truck was only a couple of years old i had to replace the cataletic converters ,the mech told me bad gas ,is this true? and is this part of my p420...

Code p420 is a code for catalytic converter enefficiency. This can be caused by a few problems. The vehicle uses two sensors one before and one after the cat. The sensors determine how well the cat is doing its job based on how much oxygen is sensed in the air based on the rule of thumb of 21% in our atmosphere. You mentioned that these were replaced once before, and i hate to knock another technicians work without seeing it but it could be possible that the cats he installed were not OEM parts and just a generic. You can get this code from using a non vehicle specific part like that, aseasily as you can get it from a faulty pre or post cat o2 sensor.
best thing i can suggest is getting the car on the scanner and having a buddy drive it on the highway at a steady rpm, watch the 02 sensors and see if there is erattic movement or sticking, from there we can findthe next step, and FYI all catalytic converters come with a Federally Mandated Warranty period of 8 years 80,000 miles, so dont ever pay for new ones again.

Aug 27, 2009 | 2005 Dodge Ram 1500

1 Answer

1998 CIVIC P420 CODE

the cat is bilt into manafold and the sencer is just up abuve it

Jun 19, 2008 | 1998 Honda Civic

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