Prius (2004-09) :: 2005 - Error Code P0420 / CEL Came On Again?

Just picked up a 2005 with 146k and full Toyota service history, although seems a steering recall was not done. Will run it to the dealer today to check. I need to decide a.s.a.p. if I am keeping the car or not (I know the seller, he will take it back)

Anyway to cut a long story short, two questions.

1) Car had P3190 and P0420 when I got it. Seller reset, drove home and within 5 minutes on the road the CEL was back on. Checked the codes at home and see only a P0420. Much to worry about? Seems this might be big (Cat) or small (O2). Car getting great mileage - 60mpg at 60mph and it seems to be running great. Should I worry or forget about it? Note I am in Florida with no inspections.

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Prius (Gen 2) :: Power Button Didn't Work For A While - CEL On With Code P0420

The power button didn't work for a while: For about two hours, the power button (and other stuff) on my 2007 Prius didn't work. But, after a couple of hours, the button worked again and I was able to power down my car (this after many, many pushes both soft and hard). I've now turned it on and off a few times and the car seems to be OK and it's behaving as if it's smiling at me and saying, "What?"

My questions: Does this happen a "lot"? Would the car have turned off if I turned off the smart function (as described on page 34 of the manual)? Is this issue as serious as it seems? Should I dump the car?

This is the first time in 138K miles that the below issues have manifested separately or together.

Other issues that happened at the same time (this morning when the car didn't turn off) were that the:

Instrument cluster was completely dark except for the check engine light (the dark instrument cluster was what first tipped me off that something was wrong)

Backup camera didn't turn on when I shifted into reverse gear

Phone didn't automatically go to speed dial when I was in motion

Fifth door unlock didn't work; the four doors locked/unlocked using the lock/unlock button on the door, but the hatchback didn't unlock.

A day or so ago, the check engine light came on and is throwing a "P0420" code (I posted about this separately yesterday).

By the way, I found out that if you hold down the power button for a while, the car goes into a different state of being where the ICE isn't running and the battery shows as completely empty.

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Prius (2004-09) :: 2005 - Pulled Over Error Code P0420

So I bought a used 2005 Prius back in August it had 88,000 miles on it and was out of warranty. But I had a full inspection on it and the car was in great shape. Well, after a few months of driving, I got the P0420 error. I took it into my mechanic who cleared the code and told me to call him if it came back on. It came back on, then I cleared it myself, and it came back on again. So it was confirmed that I had a bad catalytic converter.

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Prius (2004-09) :: Code P0420 - Diagnosing O2 Voltages And Cat Temperature

I have P0420 on my 06 prius with 220K miles. I reset it and it comes back after roughly 50 miles-ish. I have freeze frame data when the code is thrown. I read live data at 2500 rpm while the car is warm, and have all the data on the video link below.

My upstream O2 voltage is 3.1-3.3V. Downstream is .2-.4V. I understand that the downstream should be steady, and the upstream should fluctuate and read something between .1V-1V.

I have also taken thermal temp gauge and measured across both cats and readings downstream seem to be only slightly higher (+50F). It should be ALOT higher shouldn't it?

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Prius (2004-09) :: CEL On / Code P0420 / Catalytic Converter Threshold Below Efficiency

I checked out a 2006 Prius yesterday a guy is selling. It had the CEL on (not sure why somebody would try and sell a car with that, but anyway). He said that it's because they get gas at a station that consistently doesn't tighten the gas cap enough but by the time the tank is down to 1-2 bars the light always goes away. Although I don't doubt his story, I absolutely doubted the cause. So I took it to get the code pulled and it was P0420, which is catalytic converter threshold below efficiency.

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Prius (2004-09) :: 2006 - Check Engine Light - P0420 Code / Air Leak In Exhaust

So today my CEL came on. I immediately looked at my mileage and I was EXACTLY at 500m past my oil change the other day. I checked the dip stick and lo and behold, it was about 3/4" past the full marker. I took it back to the oil change place and had them drain it down to a good level.

I had driven from NH to NY this week. I filled up my gas tank on my way home from NY. Gas cap was on nice and tight for sure.

The code is still on (not sure how many miles or drive cycles is required) for something to clear. I figured it was perhaps due to too much oil added. I decided a few hours later to take it to AutoZone and grab the diagnostic code. It's a P0420 code (Cat System efficiency below threshold: Air leak in exhaust before rear HO2S, AF Sensor Error, Fuel System Fault, Faulty Catalytic Converter).

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Prius (2004-09) :: Check Engine Light Coming On And Off / Showing Code P0420 For Catalytic Converter

My check engine light has been coming on and off and it seems to show P0420 for catalytic converter. The light stays off for about a week and it'll come on for a day or two and off again.

Wouldn't a failed converter stay failed? Can P0420 be triggered by loose/bad gas caps?

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Celica :: 2000 GT - CEL Pop Up / Code P0420

I was just driving and suddenly i had my CEL pop on. I went to pepboys to have them read the code for me and it Came up P 0420. I have been looking up the code and got a few emissions issues but not sure what one to do first. Any link with Main issues for CEL Codes? Or know what it could be?

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Passat (B5) :: P0420 Malfunction Code

While on business travel, my wife's 2003 1.8T Passat wagon had the MIL illuminate. I had her pull the OBD2 code while I was away, and it came up with P0420. I have been reading up on it, but I have found much in the way of troubleshooting this code. I don't want to just start randomly replacing parts until the light goes away. When I get back I am going to look for exhaust leaks, but barring those what else can be looked for.

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Golf/GTI VI :: USP Down Pipe With P0420 Code?

I have the CBFA motor, and i am getting getting the p0420 error code. I have read two related threads here and here about p0420 codes and different downpipes. It seems the AWE and Nuespeed seem to be better for getting around CEL without additional flashes. I currently have purchased and installed one RAI straight O2 spacer (after the cat) and have tried both the medium and smallest insert but after clearing the CEL it has returned both times with the same code. Do i need two O2 spacers, one installed with the smallest insert and another with a different size? Trying to make sense of all the posts.

I am unitronic stage 1, before going stage two i want to have the CEL under control so i can downgrade the flash and not trip CEL for smog.

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GTI 337/20th Anniversary :: Keep Getting CEL / Code P0420

I have Unitronics Stage 2, and a 3" downpipe... I keep getting a CEL P0420. I know its about the second o2 sensor, but I don't understand why I am getting the CEL with my chip? Could it be possible that when I put the downpipe back in i reversed the 2 sensors? Or are they the same...

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Camry :: When Drive Over 80 Mph Within 15 Minutes CEL Comes On With Code P0420

2006 Toyota Camry LE (4 cyl) with 149,500 miles. All maintenance up to date.

Over the past month, anytime I drive over 80 mph within 15 minutes, the CEL comes on with the code P0420. I read the code and erase it. The funny thing is typically I'm getting very good gas mileage during that tankful when the CEL comes on. I've read that it is likely the downstream oxygen sensor and I plan to replace it. (In February, I replaced the air/fuel sensor). My two questions are:

a) What is the part number for the oxygen sensor (non-California emissions)? I want to make sure I get the right part.
b) Why the CEL comes on after travel over 80 mph? Is this coincidence or is there a reason why this happens?

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Nissan - Maxima :: 2005 - Got P0420 Code

Keep getting the P0420 code on this vehicle. Have changed air filter, spark plugs, run fuel injector cleaner through the tank on Shell 93 octane fuel. Drove 430 highway miles to clean out the carbon and the SES light is still on and when we check the code it says Catalyst system effiency below threshold bank 1. How do i get this fixed?

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Toyota - Tacoma :: OBD2 Gives Same Code Twice - P0420?

My Toyota Tacoma is reporting (via an affordable OBD-II scanner) the same P0420 code: First as a regular code, then as a pending code. What could that mean?

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Golf V R32 :: Got CEL And P0420 Code After Engine And DSG Flash

I've had both the engine and DSG flash from UM for over a year. The other day I got a cel and a p0420 code. I still have stock dp and oem cats (only Borla cat back). I know the cats are still under warranty (8years 80,000mile). My question is if I bring the car to the dealership for cat warranty will they be able to detect the um flash and use it against me to fix the cat problem?

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GTI 337/20th Anniversary :: CEL Came On After DV Switch Replaced - Code P0420

So I recently (within the last month) replaced my DV for a Forge 007 and my stock air box for an EVOMS v-flow. My cel came on after the DV switch and was throwing the P0420 code at me. Then I swapped the intake and it has been good but I felt like I was running a bit rich and pulled my codes and it now has P0030 in addition to P0420. Why this is? I have 88K miles. Spoke to a mechanic and he says he thinks it is my cat dying. I'm a bit confused since I have a turbo back exhaust.

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Golf VI R :: 2009 TDI - P0420 Catalytic Converter Code

Does this mean the DPF is shot? I believe its integral with the cat. whats worth checking first?

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Golf IV / Jetta IV :: Getting Error Code P0420 Intermittently?

I keep getting the error code P0420. Cat below threshold.

I have replace both the front and rear O2 sensors and we reset the check engine light. While driving through the cycles to reset the sensors for them to be ready for DEQ, the check engine light came on again.

I am about ready to buy the Cat Converter, but it is really expensive and if there are any other things that I can try before replacing the Cat I would like to try that first. Any other issues associated with that code, or should I just replace the Cat Converter as my next step.

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Pontiac - Grandam :: 2001 Getting OBD Code P0301 / P0420?

We bought a used 2001 Grand Am (V6 automatic) a few months ago. Mileage was just under 100,000. It was running decently at first, but that improved once we did more maintenance. It's gone from about 150 miles on the highway on a full tank to about 250. A lot of the problems didn't reveal themselves until we took it onto the highways. These are the parts we changed in the last 2 months:

-new battery (old one was 0.1 above fail)-all 6 spark plugs-catalytic converter-front oxygen sensor-oil filter-timing belt-pcv valve and breather hose (old one melted)-all 4 shocks/struts

Latest problem is OBD code P0301 cylinder #1 misfire. The entire car started to shake when we were in low speed in a drive thru. It only seems to shake in drive gear and it does it the whole time. It doesn't shake in reverse or any other gear. Found out #1 spark plug was cracked and a chunk of the ceramic portion was missing. It got replaced but that didn't fix the problem. Haven't noticed any white exhaust yet. The ignition fails 1/7 of the time since P0301surfaced.

The last problem we had was P0420. We went to 3 different shops and nobody was able to fix the problem properly. It wasn't until the pcv valve and breather hose were replaced that the code disappeared. The valve was actually cracked and parts of the breather hose were melted. I can't understand why nobody noticed that.

I know there could be a lot going on, but I was hoping the possible problem could be narrowed down.

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