Question about 2000 Mitsubishi Eclipse

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Code Po420 on my 2000 eclipse

This Po420 code keeps coming on. its says my effeciancy is low in bank 1 it gave me thinks that could be the problem cat, o2 running condition.

well replaced the cat right when the light came on and it was good for a month than came back on.

than i replaced the o2 sensor and it is still on i dont know what it could be?

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6 Suggested Answers

countrysi248
  • 443 Answers

SOURCE: 98 silverado codes po420,po430,po446

if the cat was pluggin you would see this as your going down the road it would not get to top speed .. They act up usually only run 40 top speed.

Posted on Apr 12, 2009

CMV9
  • 594 Answers

SOURCE: Pulled code p0420 on 99 chevy astro, 2wd, v6

from what i am finding the code means o2 sensors. they recommend replacing them and if this does not work than replacing the cat converter

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.

causes

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
  • Retarded spark timing
  • The oxygen sensors in front and behind the converter are reporting too similar of readings
possible soloutions

Some suggested steps for troubleshooting a P0420 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.


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Posted on Aug 20, 2009

  • 8 Answers

SOURCE: I have an '01 Galant

Im pretty sure the bank 2 is talking about by the catalitic converter and since is sensor 1 it should be before the CAT otherwise it should be on the exahust manifold prolly in the back of the engine.

Posted on Sep 19, 2008

  • 279 Answers

SOURCE: 01 Eclipse GT - bad o2 sensor heater circuit (bank 1 sensor 2)

Your question was truncated. I see that the bad sensor is on bank 1, but I can not see if it is the upstream (sensor 1) or downstream (sensor 2) sensor. The upstream sensors are mounted in the exhaust manifolds (look sort of like spark plugs) and have wires going to them.
You will need a 7/8" or 22mm wrench to remove the sensor (after disconnecting the wires). If your car has over 70,000 miles I STRONGLY suggest that you replace BOTH upstream sensors. One in each exhaust manifold.
Charlie

Posted on Dec 23, 2008

polarcycle
  • 1392 Answers

SOURCE: PO420" Catalyst efficiency low Bank 1"

Replace the catalytic converter.

Posted on Mar 10, 2009

  • 31 Answers

SOURCE: o2 sensor bank1 sensor 1

usually bank 1 sensor one is closest to the motor(guess) but you can look it up in a manual and just changing the 02 sensor is gonna fix it they are anywhere from 40 to 100 dollars hope it helps

Posted on Jul 09, 2009

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