Trouble Code: P0420
Catalyst System Low Efficiency (Bank 1)
Possible Causes:
Air leaks at the exhaust manifold or in the exhaust pipes
Base engine problems (i.e., high engine oil or coolant usage.)
Catalytic converter is damaged, contaminated or it has failed.
Continuous engine misfire conditions, or weak or low coil output.
Front HO2S or rear HO2S is contaminated with fuel or moisture.
Rear HO2S is loose in the mounting hole (check it for a leak).
Front HO2S older (aged) than the rear HO2S (HO2S-12 is lazy) .Here is what is listed in the Saturn repair guide.
Testimonial: "So should I change the front also? The front looks new so that is why we didnt touch it. We only bought and changed the rear because the rear looked rusted and burnt and was fused into the muffler. So should I change the front as well?"
Check your exhaust system for leaks.I don't want to tell you yeah to changing and it not that,also it states the Catalytic converter could be bad.I guess only one way to see is change it.To check Catalytic converter ,go to midas,they will check the whole exhaust for free,they also may have a scan tool that directly tells what the problem is.Replacing parts is expensively more if problem isn't solved.
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SOURCE: 2003 Saturn L300 indicator lights stay on: ABS, SES...etc
first problem, went to autozone. the guy that looked at your car was making pizzas last week. they pull codes and sell you every part you will buy. take the car to the saturn dealer and replace the bcm.
SOURCE: 98 F150 idle drops, almost stalls
VERY COMMON ISSUE AT THE FORD DEALER I WORK AT, HERE IS WHAT i DO TO FIX IT. THIS WORKS 90% OF THE TIME, IT IS NOT A CURE ALL FOR STALL SLOW IDLE BUT A CLOSE SECOND.
Here are some of the causes of surges, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.
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
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:
possible soloutions
Some suggested steps for troubleshooting a P0420 code include:
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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SOURCE: 2000 Subaru Outback Wagon (100K miles) with P0420 Code
I do not know for sure if this is the problem you are having, But, I have noticed that from 95 up to 2002 I have seen a lot of PO420 codes that have been just the sensor. I do not know if it was a weak sensor or just that program telling it that it is below threshold. I did notice that if the vehicles are run for a long trip at highway speed it goes out. I wish you luck and have a great day.
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Ok Guys........Thank you so very much....... It ended up being the front sensor that was bad. Got it changed and got my 42 miles per gallon back!!! WooHoo!!! Also lubed or oiled the A/C compresser thingy and she no longer squeaks and the SES light doesnt not come on no matter how hard I put the petal to the metal!!!
Good job,saved money doing it yourself.
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