Golf IV / Jetta IV :: 2001 - Intermittent P0420 Cat Below Efficiency Code Appears
Jan 4, 2015
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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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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My 2005 Dodge Dokota 4.7L V8 152,000 miles has an intermitent check engine light (CEL) code P0420 ('catalylst efficiency') that turns itself off.
1) 151,000 CEL on, code P0420, checked, cleared at dealer.
2) 151,948 CEL on, code P0420, checked, cleared at dealer (Cat Conv).
3) 152,200 CEL on, code P0420, checked, cleared at local auto parts store.
4) 152,597 CEL on. No checks.
5) 152,815 CEL turned off on its own
6) 152,849 CEL on. No checks.
7) 153,137 CEL turned off on its own.
Twice in this time CEL has came on soon after a fill up from near empty.
Engine runs fine, 18-19 mpg highway.
Have seen numerous on-line reports of other possible causes:
a) base engine problems (coolant or oil) -- coolant temp sensor
b) Air in leakage -- air systems or manifold
c) Lazy front O2 sensor
d) fuel pumps
e) timing or misfire
f) what else? - (gas cap, other...)
What to check first or categories to eliminate?
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P0420 code. Catalyst Efficiency Below Normal (Bank 1)
This was the explanation I got from autozone. First question is how serious is this? The car seems to drive fine and normal, but I just purchased this car about a month ago. The light turned off after the guy at autozone plugged in the scanner. I am sure it will come back on again after some driving. Is it ok to drive with it on?
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Recently I pulled code P0420, AKA Bank 1: Efficiency Below Threshold.
To start from the beginning...several weeks ago my EPC light came on so, like most educated consumers I decided to buy a vag-com. I pulled the codes and got both the Bank 1 and Bank 2 efficiency below threshold codes (p0420, p0430). I reset the light and literally within 3 minutes the EPC light came back on only this time just Bank 1.
So I drove around again for a week and the check engine light came on this time, back to Bank 1 and Bank 2. Whether trying to replace the spark plugs will possibly fix the misfires, its Cat Converter replacement or possibly just replacement of 02 sensors. I have been reading mixed responses.
FYI I use synthetic oil and chance the oil every 7500-9000 miles, have 89,000 miles and have never changed my spark plugs.
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P0420 Catalyst System below efficiency -- bank 1
I've had this code for a couple months trying to trouble shoot it. My gas mileage has been affected, as I'm getting about 23/24 MPG city/highway. I replaced the upstream 02 sensor with am aftermarket Bosch variety( I'm not sure why a non-OEM one would make a difference, as long it's working correctly).
My car has 253k miles, the cat doesn't rattle and I don't smell any rotten eggs or anything, but it has to be clogged or the 02 sensor I got was defective. My engine runs fine and I don't have any problems accelerating or decelerating. It may still be the 02 sensor since the gas mileage decrease is so significant, or it could be my converter is really clogged up.
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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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I have been getting a CEL P0420 for low cat efficiency bank 1 on my 2002 Ford Escape V6. The truck runs fine otherwise. I have ran two loads of Cataclean and the light keeps coming back a few days after CEL reset so I am pretty sure one of cats is done. I am going to replace with an aftermarket cat. My question is, with this code, do I need to replace the front exhaust manifold cat or the rear manifold cat?
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I have a 2006 Subaru Forester with 95,000 miles on it. Earlier today the CEL (solid) and cruise (flashing) came on while I was driving. I believe it may have occurred as I was accelerating up hill. I filled up yesterday, so I tightened the gas cap when I stopped. On my way home, I stopped by my mechanic and they read the code; P0420 Catalyst Efficiency Below Threshold Bank was the code that was read. They reset the code for me but told me that the catalytic converter is what needs to be replaced.
My question: Could the light coming on be incidental (i.e., is it possible that it was a "blip" and my catalytic converter is okay?)? My mechanic said he thinks it is, and that my car should last me quite a bit longer. I am asking because I've put in a bit of money into the car of late and I'm wondering if I should just jump ship. I should say that the majority of the repairs are maintenance (e.g., brakes, tires).
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Book says "catalyst system efficiency below threshold (Bank 1)".. Is it just based on mileage or an actual bad O2 sensor or other bad system component?
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I have been trowing a P0422 code which is main catalyst below efficiency.
I recently changed the rear o2 sensor and about 60 miles later the same code came back.
Logic dictates that the Cat is bad or there is an air fuel issue. No other codes have been thrown.
The car is a 1999 Jetta 2.0L AEG engine but it only has 51k miles on it. Would the cat go bad in 51k miles?
What else could I be looking at?
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I'm working on a 2003 Jetta GLI 1.8t (MT and 140,000m if it matters). The CEL has been on for a couple of weeks because of an exhaust leak throwing a catalyst efficiency code. After I make this post I'm going to run down to the advance auto I used to work at & see if I can borrow the scanner to see if there's anything new, but as of right now I don't know. I'll update the thread if I find anything.
The car started yesterday AM perfectly fine. Started again when I left work around noon. No problems with the start, idle, acceleration.. it's all good.
3 hours later I tried to start it to go pick up my kid from school but it just cranked without firing and would not start. I took care of business with the kiddo and then started trying to pin down the problem.
1. Opened the door & listened for the fuel pump to prime.. No sound.
2. Noticed the dome light is on.
3. Checked ALL of the fuses on the side of the dash.. All are fine. Turned key to listen for secondary prime.. no sound.
4. Bought Fuel pump relay & replaced.. no change.
5. Cursed.. a lot
6. Bought fuel pump.. replaced.. no change.
7. Cursed a lot more.. and cried a little too.
8. Noticed the fuel pump was now priming with the key being turned, but still not when I open the door.. Dash indicates the known CEL, but now I notice that the EPC light is on too (this could be from all the fruitless cranking drawing down the battery charge)
9. Figured I'd throw in a new crank angle sensor cuz of the EPC.. no change.
10. Shot starting fluid down the intake.. didn't hit a lick.
I feel like I'm at a dead end.. It's acting like a bad ignition control module, but there's no such thing on a vw 1.8t.
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Has around 173,000 miles, with a fresh cat installed a couple hundred miles ago. I was getting this code before, that is why I had a new cat installed. The code finally came back, and just recently I had to replace the crankshaft position sensor. After the sensor change, it was running great. The CEL came back on during a rainy day, I cleared it and was good for a few days. Then it rained again, and it came back. I couldn't afford a new OEM cat, I grabbed the best rated one I could from Amazon and had a shop install it. I know non OEM can be an issue, but I hope it is just an O2 sensor going bad.
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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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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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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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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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I recently picked up a 2001 MK4 jetta and Have some issues with door locks. Upon searching I'm thinking I may have a faulty door lock module.
Symptoms are that the doors will randomly lock for no reason when I unlock the door and sit inside for a min or two. PO broke the drivers armrest control and glued them in place and I think some glue seeped into the lock button as it is very stiff and no longer works. Going to replace the door card and controls but wondering if the problem may be due to typical burnt out soldering points?
For my window issue, passenger window appears to possibly be crooked in the window clips as it stops 3/4 of the way up and will reverse back down as if stuck. I have to keep pressing it to get it to go up. Does this sound like typical broken clips and glass is about to fall? Would I just undo clips and reattach?
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My 2004 Outback now has 120K, has always been maintained and repaired at the dealership (except tires and battery), and has always run great! I've had the plastick-y parts replaced over the last few years including head gaskets when one cracked and made smoke. In July I got a jump from a AAA tow truck, who said my battery tested as needing replacement.
In September my check engine light went on, and the dealer found the code PO420-catalyst system efficiency. They didn't seem to look any further into causes. The cat converter replacement was to cost $2521. They reportedly tested the battery as OK as part of their routine checkup. I declined the new cat converter till learning more. Meanwhile, my check engine light seemed to cycle on, then off, then on, then off . . . every several days.
In December I had the battery checked at Sears, who replaced it under warranty. So I guess it wasn't okay after all. After that my check engine light stayed off for somewhat longer than usual, then back on for most of January. I was just about to give in and get the repair done when it cycled off briefly a few days ago.
I've lost trust in the dealership because of their battery check which differed from others before and after theirs; and for their lack of specific diagnostics. The light is back on and I don't know what to do next.
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My 2005 Dodge Dokota 4.7L V8 152,000 miles has an intermittent check engine light (CEL) code P0420 ('catalylst efficiency') that turns itself off.
1) 151,000 CEL on, code P0420, checked, cleared at dealer.
2) 151,948 CEL on, code P0420, checked, cleared at dealer (Cat Conv).
3) 152,200 CEL on, code P0420, checked, cleared at local auto parts store.
4) 152,597 CEL on. No checks.
5) 152,815 CEL turned off on its own
6) 152,849 CEL on. No checks.
7) 153,137 CEL turned off on its own.
Twice in this time CEL has came on soon after a fill up from near empty.
Engine runs fine, 18-19 mpg highway.
Have seen numerous on-line reports of other possible causes:
a) base engine problems (coolant or oil) -- coolant temp sensor
b) Air inleakage -- air systems or manifold
c) Lazy front O2 sensor
d) fuel pumps
e) timing or misfire
f) what else? - (gas cap, other...)
What to check first or categories to eliminate?
View 4 Replies
