Question about 2000 Toyota 4Runner

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0420 AND CHECK ENGINE LIGHT STAYS ON

REPLACED O2 SENSOR REPLACED AIR/FUEL SENSOR PUT 92 OCTANE WITH CLEANER ADDITIVES FOR INJECTORS ETC. LIGHT STILL COMES ON AFTER COUPLE DAYS 0420 PENDING LIGHT & 0420 LIGHT AFTER FEW DAYS ARE CATS THE PROBLEM OR IS THERE ANYTHING ELSE TO CHECK.

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  • Toyota Master
  • 17,970 Answers

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.

Posted on Feb 17, 2012

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Posted on Jan 02, 2017

afarri
  • 1386 Answers

SOURCE: my 2003 toyota matrix has a check engine light

Hello and welcome to FixYa!

Yes indeed. It can be a bad coil. This is common on this car specially if the check engine light doesn't go off after the O2 replacement. Have it replaced and I believe you'll be good.

Hope this helps and thank you for using FixYa! Have a good one!

Posted on May 21, 2011

dttech
  • 4803 Answers

SOURCE: using more rpm to maintain

If the RPM is higher at any particular speed than before, the only cause could be that the transmission is slipping. Things like O2 sensors, Catalytic converters, fuel treatments, etc. have absolutely nothing to do with incresed engine (input) speed to axle (output) speed ratios.

Posted on Aug 06, 2011

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