Question about 2000 Lincoln LS

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2000 Lincoln Ls V8 still getting code PO420 after replaceing Cat Conv,changed 02 sensors, still getting code PO420 and now when exiting the freeway the car turns off.... have to put it in park to restart and its fine, this has happened like 5 times already???Pleeease help? i really need info as to exactly what is wrong, what to do.... i'd really appreciate your help....:)

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Check your MAF sensor readings. ( MASS AIR FLOW ). You probably need to clean out your throttle body. If it's not reading properly, it could def. kill your car. Hope this helps, James Booth. Please rate this. :))

Posted on May 20, 2011


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Location of 02 oxygen sensor on 00 Linc ls v8 need replacing

O2 sensors are after the cat converter and if you have 2 cat converters they will be after each converter
have you had the fault codes read to get that code or are you guessing that that is the problem
mostly with O2 sensors a wash and scrub in vinegar will get them working again but the HO2S sensors ( heated sensors ) in front of the cat converters give the most problems from the current in the wires or other circuitry faults
run the fault codes and save money

Oct 22, 2015 | Cars & Trucks

1 Answer

2000 Lincoln Ls V8 still getting code PO420 after replaceing Cat Conv,changed 02 sensors, still getting code PO420 and now when exiting the freeway the car turns off.... have to put it in park to restart...

Could be a fuel pump issue, there was a tsb on fuel pumps going bad, although it was usually a problem with the jet pump. The main fuel pump, in the left side of the tank as I remember would pump it dry, and the jet pump wouldnt pump to the other tank, therefor over heating and possibly popping the fuse for the fuel pumps. You can take the lower part of the back seat out and then gain access through the floor to the tanks. id try to change the fuel filter first. It could also be a regulator or injectors

May 20, 2011 | 2000 Lincoln LS

1 Answer

Changed cat conv, changed o2 sensors, code PO420 keeps showing up so does check enginelight????? new problem now, when exitiing the freeway car shuts completly off??? its done this a few times now. i have...

Some cars can not have a generic converter put on them. Replacing this and the 02 sensors should have fix the code problem. Depending on your car I would check the converter. And if you had it done at a shop take it back. If your car has to have a specific converter and it got a generic one, this would eventually cause the car to stall.

May 20, 2011 | Lincoln LS Cars & Trucks

1 Answer

My 2003 Lincoln Aviator emissions light is on and I failed inspection because of it. How can I pass inspection and fix this emissions problem? The inspection code given to me was PO420???

po420 is catalyst system efficiency below threshold. meaning is--- could be down stream 02 sensors or a bad convertor. try buy replacing down stream sensors, hopefully this may help. ( down stream 02 sensors are between convertor and tailpipe). have a good day !!

Dec 13, 2010 | 2003 Lincoln Aviator

1 Answer

2003 lincoln ls what does the codes 420 and 430 mean

PO420--Catalyst System Efficiency Below Threshold (Bank1)
PO430-- " " " " " (Bank2)

O2 Sensor
Coolant Temp Sensor
High Fuel Pressure
Bad Converter

Owning a 2004 V8 myself--I will say your need to go thru the entire engine, as to how it is running
It may be overheating due to coil misfires or other issues and ruined the

You need to solve all issues before replacing a converter
I would stay far away from a dealer, unless you have a couple thousand to spend

Nov 02, 2010 | 2004 Lincoln LS

1 Answer

Code po420 on scan tool but o2 sensor was replace 2 months ago

Hello and welcome. the code P0420 is for a bad cat. converter. replacing 02 sensors wont repair this code. the code simply's means that thje cat. converter is not working as designed and will need to be replaced.

The PCM determines the oxygen storage capability of the catalytic converter has degraded below a calibrated threshold.

Jul 03, 2010 | 2004 Mazda RX-8

2 Answers

Check engine light on PO420 code ? recalls

Huge problems with these cars. The Pre-cat converter is built into the exhaust manifold. Expensive to replace. No Recall on this item. Some say that inferior compounds in the catalyst cause corrosion and early wear of the piston rings. I have seen one of these use 5 qts of oil in 300 miles. Is this car using excess oil?

Jan 16, 2010 | 2005 Nissan Altima

2 Answers


I can try to help. The chk engine light is generally tripped by the #2 02 sensor. The one after the cat converter. It 's purpose is to monitor the efficiecy of the cat converter. You state there is a power loss problem also. This loss of power is common when the cat converter is restricted and the exhaust can't escape as fast as needed. . You can tell the converter is bad by a sulphur smell in the exhaust, a wheezing at the tail pipe, Or, the exhaust does not immediately stop when theengine is turned off. Good Luck. Have the cat conv checked and replaced . I hope yhis is the help you needed, Ned

Nov 05, 2009 | 2000 Lincoln LS

2 Answers

Fault code po420 ; is problem sensors or is it the cat conv

The only thing that will set this code is the catalytic converter or the oxygen sensor behind it. Way to tell if it is the sensor is to monitor voltage reading with scan tool and see if it is fluctuating the same as the upstream oxygen sensor. If it is the converter is "free flowing" and will have to be replaced. If the sensor is "flatlined" then it is most likely bad and setting the code.

Apr 30, 2009 | Ford Fusion Cars & Trucks

1 Answer

The code PO420 came on for my 2000 Toyota Camray ......

Catalyst Effeciancy below threshold (Bank 1) is the code meaning. Check or replace the oxygen sensors. Some cars have 2 .One is on the front of the cat. the other is the on the back. Check the back sensor . Other possible causes are leaking or damaged exhaust manifold, bad coolant temp sensor.If toyota did not replace both . replace the one on the back of the Caty.

Feb 02, 2009 | 2003 Toyota Corolla

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