Question about 2001 Toyota Celica

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Replaced catalytic converter auto zone generic and both oyxgen sensors still 0420 code below treshold after 37 miles from clear, could it be running too rich at 165K miles

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  • John Mcnall Oct 03, 2010

    what about injecter cleaning if not spraying nice mist of fuel

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This code is generic and is the same on all vehicles.

P0420 = Catalyst System Efficiency Below ThresholdCatalyst System Efficiency Below Threshold.

This means that the secondary O2 sensor detects that the catalytic converter isn't working as efficiently as it should.

This engine code can be triggered by any one of the following:

1.) The catalyst in the catalytic converter is cracked, clogged, or otherwise damaged.
2.) The secondary O2 sensor is malfunctioning.
3.) There is an exhaust leak.
4.) The computer unit is faulty

Posted on Oct 03, 2010

  • INDIRA KUMAR
    INDIRA KUMAR Oct 03, 2010

    It can cause the problem but it is not so persistent...

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Why Did the Vsc and check engine light come on in 2005 toyota highlander?


The converters generally fail only after the truck has been running rich. I would not replace them until certain the engine is running properly. There is no harm to the car to drive with these converters. Was there any history of rich operation codes?

Jul 08, 2017 | 2005 Toyota Highlander

1 Answer

0420 AND CHECK ENGINE LIGHT STAYS ON


DTC P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

You will likely not notice any drivability problems, although there may be symptoms.

A code P0420 may mean that one or more of the following has happened:
Leaded fuel was used where unleaded was called for
An oxygen sensor is not reading (functioning) properly
The engine coolant temperature sensor is not working properly
Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
******** spark timing
The oxygen sensors in front and behind the converter are reporting too similar of readings

Some suggested steps for troubleshooting a P0420 error code include:
- Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
- Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
- Inspect the downstream heated oxygen sensor (HO2), replace if necessary
- Replace the catalytic converter

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Feb 17, 2012 | 2000 Toyota 4Runner

3 Answers

My check engine light came on and I took the car to the auto parts store and they diagnosed it as the catalytic converter. I stopped driving it for a few months took. Then I took the car for an...


What was the exact code? The O2 sensor after the Catalytic Converter, or Rear O2 Sensor, could be faulty which would cause the computer to think the Catalytic Converter is not working efficiently. The code can be reset at the auto parts store with the same code reader they used the first time. P0420 is the most commonly thrown OBDII code pertaining to catalytic converter efficiency below threshold. I would replace the O2 sensor after the Catalytic Converter and reset the computer to see if the code comes back. If it comes back you may have a bad catalytic converter, exhaust leak, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter, etc.

Apr 26, 2011 | Nissan Altima Cars & Trucks

2 Answers

Hi, I need to take my 2001 Mazda 626 4cyln for SMOG check in CA. But its check engine light is on, diagnosed as code P0421. Appreciate your help to fix this problem, or just to pass the check. Thank you.


CODE P0421. DEFINITION-CATALYST EFFICIENCY LOW-BANK 1. EXPLANATION-THE OXYGEN SENSORS MONITOR THE CATALYTIC CONVERTERS ABILITY TO STORE OXYGEN. PROBLEM CAUSES- 1. CATALYTIC CONVERTER DEFECTIVE (FAILURE POSSIBLY DUE TO #2,3, OR 4) 2. ENGINE MISFIRE OR RUNNING CONDITION. 3. LARGE VACCUM LEAK 4. ENGINE OIL LEAKAGE INTO EXHAUST-VALVE GUIDE SEALS, PISTON RINGS. THE PCM HAS DETERMINED THAT THE WARM UP CATALYST EFFICIENCY FOR BANK 1 IS BELOW TRESHOLD FOR THE CURRENT ENGINE OPERATING CONDITION. (BANK 1 IDENTIFIES THE LOCATION OF CYLINDER #1, WHILE BANK 2 IDENTIFIES THE CYLINDERS ON THE OPPOSITE BANK).

replace O2 sensors, or your Catalytic Converter.

Oct 06, 2010 | Mazda 626 Cars & Trucks

1 Answer

I have a engine light Code P 0420, please tell me how to fix this & what is this. Its 2000 Honda Civic Ex $ door Sedan


Your Honda is probably very high on mileage. The P0420 code indicates that the catalyst system is operating below the efficiency threshold. In English, your sensors are telling your ECU that the catalyst in the catalytic converter is worn out. A new catalytic converter is going to be big $$$.

It is not going to disable your car, but if you live in a state requiring emission testing to pass inspection, your car will probably not pass the next inspection.

You can get a code reader (the Actron CP9575 or CP9175; both work well for less than $150.00 USD) from most auto parts stores or Sears and try clearing the code. In all liklihood, clearing the code this way will not fix the problem and the CEL will illuminate again.

Jul 21, 2010 | 2000 Honda Civic

1 Answer

There does not appear to be anything wrong but the light came on we took it to Auto Zone to get a reading and the code isCatalist effiency- low-banl 1


Hi:
Usually that code is checking the difference between the oxygen sensor before and after the catalytic converter. It is usually fixed by replacing one or both oxygen sensors, or often the catalytic converter or converters can be bad too. The best bet is to clear the code and see what comes back....

Mar 24, 2010 | 2003 Chevrolet Blazer

2 Answers

Bright red catalytic converter . I am having problems running the car when it idles it wants to kill. Tonight I noticed the catalytic converter was bright red when I returned.


The converter is clogged replace it.You probabley are getting less fuel mileage then usual and your car is probabley running hotter.

Jul 29, 2009 | 1992 Oldsmobile Bravada

1 Answer

Catalytic converter is bad on 1995 Subaru Legacy L Wagon


dearship parts are high.you can buy a factory catalytic converter or universal converter cheaper at auto parts place.they basic the same parts the.dealership has same catalytic converter.they put their price and labor rate charge an hour your pocket book will be empty.i have used universal catalytic converter.had no problem with it.the only difference is universal converter body a little shorter.but has same lengh as factory.if check engine is coming on you cant turn it off .if computer showing you a code.you could have a misfire causing rich exhaust emission.that can ruin a catalytic converter have it scan.dealership charge you about $130.00 .you can have it scan at advance auto or auto zone.to see what pcm code is.it could be oxygen sensor somethinh minor.

Jul 12, 2009 | 1995 Subaru Legacy

1 Answer

2001 Honda - New Catalytics & O2 sensors -- new 0420/1739/1456


I would send the car for a smoke test for the emissions leak...Find out where the leak is comming from..Repair it..Reset the codes, then do a drive cycle and see what happens...

Jun 29, 2009 | 2001 Honda Odyssey

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