Question about 2005 Chevrolet Cobalt

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P0420 fault code.Autozone guy says it's an O2 sensor.He says it could be any one of four sensors.Can I pinpoint the sensor with just the fault code info. ?

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Posted on Jan 02, 2017

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  • 15 Answers

SOURCE: had p0420 code on buick v-6. replaced cat.

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.

Posted on Jul 24, 2009

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emissionwiz
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SOURCE: 2005 Chevy Silverado O2 sensor

I 1st need to know the codes, the O2 heaters are fused, but without the codes don't know, check the fuse box for the O2 heater fuse, if it is not blown I will try to make out what is wrong from the codes

Posted on Oct 16, 2008

  • 14 Answers

SOURCE: Check Engine Light - O2 Sensor - bank 1 running lean

you should have three oxygen sensors on your car, one for each bank of three cylinders; should be towards the Y pipe on each exhaust manifold. Additionally you should have one on the exhaust pipe before the cadilitic converter.

Posted on Nov 20, 2008

  • 66 Answers

SOURCE: O2 sensor problem

I have a 97 gmc sierra .This truck is the same as the chevy ok.Its a 350 5.7 liter 4x4 Z71.I took it to auto zone which was my first mistake.They put it the scanner and said bad O2 sensor.Ok so which one is it i said.They dont know.Well there four (4) O2 sensors in this truck i hope you know that.I had to replace all four of them before i had to take it to a real shop.It seems the fuel pump i replaced a week earlier with an auto zone fuel pump was bad.Ive changed my feul pump 4 times now and have 235000 miles on still running.You need to get your fuel pressure checked.It should be 65 psi to start it and 55 psi to run it.If the pressures are good it could be a different O2 sensor or maybe the mass air flow senor.My last option would be the fuel pressure regulator because it seems to be a waste of time and money.I would get that fuel pressue checked first.Good luck.

Posted on Nov 25, 2008

warlock61
  • 659 Answers

SOURCE: more 99 cougar problems

there is a fuse for the o2 heaters if one of the sensors blew the fuse they will all be out

Posted on Mar 01, 2009

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2 Answers

What means catalyst Efficiency below normal


      Got it scanned and it's P0420: Catalyst efficiency below thresholdbank 1. They said it could be a bad catalytic converter or oxygen sensor. I borrowed a scanner and tried to measure the oxygen sensor readings over time.Sep 8, 2011

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Jan 26, 2016 | Cars & Trucks

1 Answer

Code p0130 & p0150


codes 130 and 150 indicate a malfunction in the upstream oxygen sensor circuit which is affecting both oxygen sensors. This fault does not directly pinpoint the o2 sensors as defective, more diagnosis must be performed to get to the root of the problem. You could have a condition where power is not reaching the sensors, causing them to appear dead. There may be a fuel or airflow related issue causing the sensors to report abnormal readings.

To answer your question, the o2 sensors in question are between the engine and the cat convertor in the exhaust. Whether or not changing them blindly will fix your problem is another question.

Jan 11, 2015 | Cars & Trucks

1 Answer

2004 hyundai elantra sedan check engine light on, 1st try at autozone gave P2251 followed by P0420, I reset the car computer to check if it comes back and it did after nearly 100 miles. second try at...


The codes that i have pulled out relates to Oxygen sensor and Catalyst converter faults.
P0420: Catalytic converter system,Bank 1,efficiency
below threshold.
P2251: Heated Oxygen Sensor (H02S)1, Bank 1, negative current control open circuit.
But not necessary the faults. You need to run the scope to see wht patterns u get on the oxygen sensor, and on the obd scanner you may be able to pick up oxygen sensor coming on and going off or rich or lean mixture and the mvolts of the sensor. Also check if the wires are not broken on the sensor. Sometimes a clogged O2 sensor can cause these problems.

Aug 13, 2014 | 2004 Hyundai Elantra

1 Answer

2001 Toyota Camry - check engine light on - code p0420 - took to mechanic and he just hooked up code scanner and gave p0420 code - without checking anything else he said rear O2 sensor needs to be...


Hello: Code 420 normally indicates a catalytic converter is operating below 60% efficiency. You need to take your car to another shop and request a COMPLETE diagnosis not a dart board guess.

Sep 13, 2011 | 2001 Toyota Camry

1 Answer

O2 sensor problems o2 sensors set po 420 code. both sensors have been replaced


The problem is NOT the O2 sensor, this code (p0420) indicates: P0420 Catalyst System Efficiency below Threshold(Bank1)

Jun 29, 2011 | Hyundai Elantra Cars & Trucks

1 Answer

How many oxygen sensors are on a 1999 chevy blazer?i found 3 one on each manifold before the cat and one after the cat. but the guys at the local auto parts store said that there are 4 total. am i missing...


if it has 2 cats then it has four sensors. i cat 3 sensors. i dought they all went bad. o2 sensor malfunction will not cause a cat efficiency belw threshold code. i would guess a baf cat on bank one.but if air pump was bad it might be poluted with carbon.try driving it hard for a bit. mabee it will clean up

May 30, 2010 | 1999 Chevrolet Blazer

1 Answer

Can I get a diagram of replacing the downstream o2 sensor


Hello adam...i suspect you are getting the P0140 O2 sensor circuit no activity (Bank 1 Sensor 2) fault code on your Kia?
The "downstream" O2 sensor will be BEHIND the catalyst converter and is tuned into the PCM map. Simply remove and replace. Typically this code is set due to a clogged or failed sensor, a poor connection, or an open circuit.
The P0420 code is typically a clogged or defective cat.
Good luck..i hope this helps..please rate me a fixya.

Jul 24, 2009 | 1998 Kia Sephia

1 Answer

2005 Ford Taurus SE 3.0L V6 OBD Codes P0171 and P0174


The P0420 code is a Catalytic converter efficiency code check the compression.Swap the #1 injector to a different location to see if the code follows.Test the coilpak. A cracked exhaust manifold is the most likely cause p0171 and 0174 Induction air leaks, vacuum or some kind fuel restriction, weak fuel pump, restricted fuel filter etc.You also could have an exhaust leak near the upstream o2 sensor. If youtake it in they will probably use smoke to find out where the leak is.

Apr 22, 2009 | 2001 Ford Taurus

4 Answers

PO420 code for 2003 Elantra


Danny,

Catalytic Converter Failure is a common cause of a P0420 Code. 1.) I would give a few calls to some muffler shops and get a thorough exhaust inspection done. As a leaking/damaged Exhaust Manifold, Catalytic Converter, or exhaust pipe could be some of the culprits as well. If it were any of those other items your car would give you a different OBD Code. Item #2.) This is not common with a P0420 Code. With the P0420 code you should have no driveability issues. (not to say that you wouldnt in an extreme rarety) Item #3.) Again this would flag an entirely different code such as P0455 (Large Evap Emission Leak) Item#4.) Engine Oil would not even set a code. I hope this helps you out, and thank you for using FixYa!

Sincerely,

JC

Nov 19, 2008 | 2001 Hyundai Elantra

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