Golf IV / Jetta IV :: Getting Error Code P0420 Intermittently?
Sep 17, 2009
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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I just bought a 03 2.0 and ive been trying to fix her back up, she is almost there, just waiting on my first gear getter from diesel geeks and trying to figure out why these codes (p0420 and p0141) keep coming back on. Originally it was just a p0420 code so i took out the upstream sensor and cleaned it, then i took out the backstream and after examining it figured it should be replaced.
I went and bought a new one and replaced it, within the next 2 days the check engine light came back on throwing the original p0420 code along with p0141 this time. So i took out the new down stream 02 sensor and took it back to autozone and they swapped it out with a new one for me free of charge. So i put the newest 02 sensor in and then within 2 days, both codes p0420 & p0141 came back on. Two 02 sensor heating wires being bad i feel is a pretty slim chance. What is possibly the cause for these two codes repeatedly being thrown?
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On my 2002 (AVH) 2.0L 4cyl Jetta I have a persistent P0420 error code: "Catalyst System Efficiency Below Threshold"
I changed the oil, cleaned the Mass Airflow Sensor, replaced the coolant, thermostat, and coolant temperature sensor. But it's still showing up.
OBDII says it could still be:
A damaged or failed oxygen sensor (HO2S)
Downstream oxygen sensor (HO2S) wiring damaged or connected improperly
Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe
Retarded spark timing
The oxygen sensors in front and behind the converter are reporting too similar of readings
Leaking fuel injector or high fuel pressure
Cylinder misfire Oil contamination
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MK4 GTi - My check engine light came on a few days ago and when I checked it, it pulled code P0420.
Just this morning, the check engine light went away.
Is this a common issue? Or should I go get it checked just in case?
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So I recently bought a GTI and started to fix a couple things. It has a P0420 code so I bought a new downpipe to install. Noticed the stock one was missing 1 of the nuts and the stud had broken off. How get this out? Do I need to remove the turbo? Looks like I do need to remove the turbo to use an extractor set.
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2001 Jetta 2.0, manual trans
I've been having problems with intermittent P0420 cat below efficiency code. Everything else is fine, no codes, runs great. I tried spacing the post cat sensor back w/ extender bung (after replacing post cat sensor..) and still get the code. I don't hear any rattling or anything to make me think cat is bad physically. I was told by dealer that a code update might resolve for $200 - which got me thinking that that if that was so, it should should be a problem which Feds should be aware.
I searched safercar.gov and found this NHTSA ID Number: 10054864
It's a service bulletin saying that VW made the limits too sensitive and it seems there was a customer satisfaction campaign to update code - pdf on site CSC-10054864-8736
It says:
May 2007
Subject: Emissions Service Action N7
1999-2002 Jetta, Golf and GTI with VR6 Engine
Update Electronic Control Module (ECM) Software for Catalytic Converter Monitoring System Dear Volkswagen Owner: We are writing to inform you of an emissions service action on some 1999-2002 Jetta, Golf and GTI VR6 engine vehicles. Our records show that you are the owner of one of these vehicles.
What Is The Problem? The electronic control module (ECM) software for the catalytic converter monitoring system is too sensitive. This can cause the MIL to come on, and some vehicles may exceed Federal and/or California emissions standards. Also, in some cases this leads to unnecessary catalytic converter replacement. What Will Volkswagen Do? Dealers will update the ECM software.
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I bought my Jetta almost a year ago, and I've been constantly replacing parts. Unfortunately, my engine misfired twice and the CEL has come on for P0420 which is inefficient catalyst. This is the only code being thrown. I've cleared it like 10 times, but it keeps popping up.
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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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So i've had this volvo for about 6 months now.I knew when I purchased it that the two codes being thrown were p0128-Engine coolant temperature, and p0420- Cat efficiency Bank 1.Inspecting mechanic said it needed a new cat to clear the p0420....I went ahead replaced the thermostat and changed the coolant to "fix" the p0128, and cleared the codes, I think the jiffy lube state inspector did not notice the that the catalytic converter test was Incomplete when he passed it. Lucky me I guess.
But now I know that I'll probably have to fix before it gets inspected again. Eventually the p0128 came back on, so I went and got a new ECT sensor. Still doesn't clear the p0128. What am i missing? Coolant temperature sits at a 3'oclock position pretty regularly and quickly. Where to start on the p0420 besides understanding its the Pre-cat o2 sensor that is throwing the code, is there anyway that these are related?
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I have a 2002 GTI 337, 1.8T and I get the faulty code P0420 insuf.cat flow?? ... it is a way arround it
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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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I was driving along today and my Check Engine light came on. I stopped at the nearest Advance Auto to have them pull the code and it came up with the P0420, Catalyst Efficiency Below Threshold (Bank 1). I asked what could cause this and they mentioned that the fuel that was put in could be causing it. They didn't mention any other possible causes. Any others? I'm thinking it could be the fuel because the last gas station that I stopped at and filled up at is one that I never go to, and maybe just got a bad batch of fuel.
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So finally got past the smog cert issue and a bad map sensor in the intercooler. However, during the smog test, I was informed I am getting low air pressure in the intake! What causes this? A bad MAF? a leak? I have replaced the EGR, and all rubber that connects hard pipes. The only piece not changed out during the rebuild is the plastic flex line from the airfilter box to the turbo intake.
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When checking my check engine light , I got P0021 a cam timing error, but my mk4 Gti runs perfectly ??
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Damn car is stuck in 3rd gear! Hooked up scanner and the screen just says error! I have to keep the scanner in the vehicle, hooked up, just to drive the car. That's just so it'll shift as its supposed to! Now it's not letting me pull the code out, in order for me to erase it! It just keeps saying "error".
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I have a mk4 jetta 2.0l with about 130,000 miles. The issue with my car is that is has a rough idle and dies out completely when I put the car in neutral. I currently have codes 16839- EVAP system leak detected, 16487- Mass air flow sensor, 17978 - Engine start blocked by immobilizer, and 16795 - secondary air injection system incorrect flow detected. The secondary air pump was taken off the car before i bought it, so i do not think that code is responsible. Also all of my spark plugs and wires are new. I think the issue is either with my maf sensor or with a vacuum line. I have tried cleaner my maf and also unplugging it, and the car still has problem. Unfortunately i do not know where all of my vacuum line are. I have only checked the two the go into the sensor on towards the firewall. The one has vacuum, but the one coming for the egr valve did have any vaccum even when i tried with my other line on it. Im not sure if this is the issue, and if it would cause my car to die.
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I was cruising down the highway and my check engine light came on. I was a few minutes from a auto store and they said my code was p1296. I found out it is either the thermostat or the coolant temperature sensor. I wanna know where it is located in the engine bay. I have a 02 VW Jetta 1.8T.
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I have a 2005 Jetta 1.8t and the thing will not start! The battery is fine, and has been recharged 100%. The fuel pump is pumping. It cranks all day, but just won't start. The only error code i'm getting is a P0411 which I understand is a leak in the vacuum system somewhere.
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2002 Jetta 1.8L Turbo running fine. Then one day driving on the freeway at about 70, I try to pass someone and notice when I push the gas the engine lulls. I back off the gas and accelerate slower and I can get up to speed. Drive it all the way home and its fine a t low speeds. Turn the car off and try to restart it and it wont start. Turns over but wont start. No CEL or anything else, I check the codes and I have a P0171 (Lean fuel Bank 1). Where do I start? Also car is parked in an underground garage. No chance of a tow out of this place, it may soon be a Jetta tomb.
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My car (jetta 2002 1.8t) have the error code p0501 even if the speedo is working. I replaced the speed sensor just to make sure.
If I erase the code, and drive no matter how far/fast I go, the check light doesn't turns on. But as soon as I turn of the car and drive again it does comes on.
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Whenever P0411 triggers for me, it is very late into driving (i.e. like 30 minutes into the freeway type of situation) where the engine has already hit optimal temperature. I've gone 1000 miles after reset before it triggers. Sometimes 200 or so miles, but it never triggers quickly after a reset. I'm unsure if it matters, but the VR6 does have a cold air intake (and I do have the breather hose connected & maf correctly connected). I'm pointing it out because p0411 became an issue about 500 miles after I had installed the cold air intake.
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