Question about 2008 Pontiac G6

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P0420 error code

I've replaced both the front and rear O2 sensors, given the car a tune up which seemed to fix the problem for a couple weeks but now its got no acceleration and the error code is back. I've read somewhere on the web that the Catalytic converter is covered under an extended warranty up to 120000 miles but I can't seem to find any concrete info on that. Any help you can offer would be appreciated.

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The fault code P0420 is caused by the catalytic converter falling below minimum efficiency level as measured by the catalytic converter monitor sensor (similar to an O2 sensor, but different function). The cat is not covered for 120,000 miles. Here is the correct information on the warranty of the catalytic converter.
The Federal Emission Warranty covers that part for a period of 8 years or 80,000 miles, whichever occurs first. So you are out by years in service and by miles.

Posted on Jul 28, 2017

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Posted on Jan 02, 2017

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  • 1 Answer

SOURCE: service engine soon light keeps coming on. Now low coolant light

I would start by doing an oil change myself so you can examine the oil and look for water/antifreeze in it. You will be able to see it separate from the oil and you can smell the antifreeze. If there is then you have a leak between the water jacket and the heads somewhere. More than likely the LOWER intake gasket is leaking into the head. You said they replaced a gasket but was it the UPPER or LOWER? If it was the LOWER did they use RTV in the correct areas? Did they torque the intake bolts to the correct pressure and install the bolts correctly? I know you don't have these answers but these could all be part of the problem. It may be leaking more at #2 cylinder and causing it to foul more than the others. Also just because a mech pressurized the coolant system and didnt see any change in pressure (hopefully he wasn't just looking for visible leaks) the issue may not happen until the engine is hot, as metals behave differently when heated, especially aluminum which the LOWER intake is made. Have a mechanic or mechanically inclined friend (gearhead) remove the #2 plug wire, then kick the engine a few times without starting it, enough to let any fluid get into the chamber, this would include gas btw. Then remove the plug and look for any wet residue on the plug, gas will evap. quickly, antifreeze/oil won't. again try to smell the residue and if necessary, lightly touch some to your tongue, antifreeze has a sugary sweet taste that is easily detectable. Remember any time you are working with chemicals such as waste oil and especially anti freeze, minimize spills and clean them up quickly and completely and place the spent fluid in a sealable container and take them to a collection center for disposal. Waste oil is a carcinagin (cancer causing) agent and antifreeze (glycol) new or old will kill any animal (child, dog, cat,etc) that ingests it. Many auto parts stores and some other retailers that sell oil and antifreeze will take your wastes if you bought the replacement fluid from them, check before you buy.

Posted on Apr 04, 2009

emissionwiz
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SOURCE: service engine light comes on , p0420 code

the light can be caused by any one or combination of over 200 trouble codes, go to any kragen or Autozone parts store and ask for a trouble code test, it is free, then record the code(s) they come up with and post them back on fixya

Posted on Apr 19, 2009

  • 28 Answers

SOURCE: p0420 fault code

you probably have to replace the catalytic converter

Posted on Jun 18, 2009

  • 462 Answers

SOURCE: o2 sensor location 1997 pontiac grand am 2.4 4 cyl auto trans

BANK 1 SENSOR 1 IS THE ONE IN THE EXHAUST MANIFOLD. BANK 2 SENSOR 2 IS BELOW THE CATALYTIC CONVERTER.

P0171 SHOULD GO AWAY WITH A GOOD O2 SENSOR BUT DO CHECK FOR VACUUM LEAKS TO BE SURE. 3.1/3.4L ENGINES HAVE A BAD DESIGN INTAKE MANIFOLD GASKET, THE LEAK OIL, COOLANT, AND AIR.

Posted on Jul 13, 2009

snafu86
  • 193 Answers

SOURCE: 2005 pontiac Grand Prix, check engine light on, Catalytic convert

Tuneup time is around 90,000 to 100,000 miles.If it were to ignition coil you would feel the misfire. Plugs, wires, airfilter and fuel filter should be changed before cat is. Plugs will tell the story.

Posted on Jul 21, 2009

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1 Answer

P0420 code


ALL TROUBLE CODES MUST BE CLEARED FROM ECM. OR THEY WILL KEEP APPEARING. A PARTS STORE CAN DO THIS, WITH U PUSHING THE CLEAR BUTTON, IF THEY WON'T.

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P0420


Hi Osar-
I pulled this link from ODB-codes.com. It lists the possible causes, diagnostics and resolution for engine code issues. Hope this helps!
P0420 OBD II Trouble Code

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Code p0420 acura m'dx


1996-newer (OBD-II) vehicles use oxygen sensors and a catalytic converter to reduce emissions. There is one O2 (oxygen) sensor in front of the catalytic converter (called upstream), and one behind it (downstream). When the engine is warmed up and running normally the upstream oxygen sensor reading fluctuates and the downstream one is fairly steady. In the case where both readings are fairly steady, a P0420 check engine light code is set.
Possible Causes: Oxygen (O2) sensor not working correctly
Damaged or leaking exhuast (pipe, manifold, catalytic converter)
Damaged catalytic converter
Diagnostic Help:
To diagnose a P0420 trouble code we begin by checking for exhaust leaks under the vehicle. Then use an oscilliscope to check the waveforms of both upstream and downstream O2 sensors. The front reading should vary, the rear should be steady. Replace as necessary. Check the rear Heated O2 Sensor. Check the catalytic converter, replace if necessary. If necessary, check for wiring and component concerns. See our article "Automotive Circuit Testing 101", if you need more assistance with this. Remember to refer to an model-specific repair manual for proper instruction.

Jan 20, 2014 | 2005 Acura MDX

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Hi, I have a 98 Honda Accord Ex V6 that showed the P0420 code and I was told that the catalytic converter needs to be replaced. So I replaced it and the check engine light came on with the P0401 code. I...


The error code p0420 does not rise only due to faulty catalytic converter but may also rise due to one of following reason:

1. Faulty rear O2 sensor

2. Damaged O2 sensor wiring

3. Exhaust leak

The error code p0401 indicates faulty Engine Gas Recirculation (EGR) valve. The remedy to the problem is:

a. Replace EGR valve

b. Repair damaged wiring of EGR valve

c. Clean the EGR valve tubing

Jun 27, 2013 | Cars & Trucks

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'01 chevy prism has the check engine light on, P0240 is the code


Hi Carla:
There are a number of things that could be causing this p0420 catalyst efficiency code. The most common thing is the catalytic converter itself is no longer functioning properly. The other likely thing is the rear O2 (oxygen) sensor is no longer working properly. Other things could include exhaust leaks, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter, etc.

A P0420 code is a trouble code on OBD-II equipped vehicles. All vehicles from 1996-newer sold in North America support this generic powertrain code. This code is a pretty common one and this site is here to help the average do-it-yourself (DIY) car owner (like you) troubleshoot, diagnose, and fix their vehicle themselves when presented with a P0420 code, saving money.

If your car has multiple trouble codes (DTC's), it's always a good idea to fix them in the order they come up on the code reader. For example, if you have these codes - P0300, P0420, P0171, then you're going to want to tackle the P0300 Random Misfire code first (resolve it), and then tackle the P0420 code, etc. The reason for that is that the first code could be causing further DTCs to be set.

If you've come to this site you most likely already know that you have a P0420 code. To start, we strongly recommend you seek the services of a professional mechanic/technician if you have any doubts as to whether you can perform the repair.

Possible Solutions: 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.

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Only a select few last 14 years

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Tune-up --- as in spark plugs?
No tune-up in my world, in the last15 to 20 years

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The computer is looking at the downstream O2 sensor (the one after the cat) to determine cat efficiency. If the downstream O2 sensor is switching simular to the upstream O2 sensor (the one before the cat) than the computer interprets this as a bad cat. The rear O2 sensor should hold a steady voltage at idle once the car is warmed up.

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