Subaru - Forester :: 2006 - Catalyst Efficiency Below Threshold Bank Code P0420
Jul 17, 2015
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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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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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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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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I have a 99 Tiburon 2.0 DOHC that I cant seem to get through emissions. The code, p0422 main catalyst efficiency below threshold bank 1 keeps popping up even after replacing the cat converter (twice) and replacing both 02 sensors. What else could be triggering this code and how to fix it?
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Have the EML on on my GS450h, read the fault codes and I have 2 fault codes that are identical (P0430). I cleared the fault codes and it stays off for a day, then as soon as I go above 60mph the next day, it comes back on again, the faults are stored and not current codes. I've not noticed any MPG loss or loss of power whatsoever! So am I safe to assume its not the catalysts? Only other thing I could think of is an o2 sensor gone bad perhaps? I don't want to spend money really as I'm about to sell the car for a more economical one for my 150miles per day commute to work! Just had all 4 wheels refurbished too which set me back a fair amount, now this!
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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've got a 2004 Prius with about 140,000 miles. Overall, the car has worked great, and I've kept up with regular service.
Several months ago, I started having bad misfiring of the engine. When I got it into the shop, it turned out to be two faulty ignition coils. The shop advised me to replace them all, which I did. Soon afterwards, however, the CEL came on, indicating a P0420 - "Catalyst System Efficiency Below Threshold Bank 1".
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CEL and VSC came on so i ran the diagnostic tool and got this msg :
P0430 Catalyst System Efficiency Below Threshold (Bank #2)
what could it be? The car performs fine, no MPG decrease, no performance impact..
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2004 F150 5.4L V8 ...
P0420 Catalyst below threshold bank ...
O2 Sensors or Catalytic Converter ...
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I was app. 10 miles from home & engine started missing & went into limp mode & yes the light flashed . I limped it home anyway & now have a PO430 code . # 2 spark plug died & caused this , danged plug didn't have a hundred miles on it since new . Replaced that plug & everything's fine except that code . Vehicle runs great . I've also read an 02 sensor could cause this code .
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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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My 1999 Camry with 169700 miles has this 'check engine light' code: "Catalyst system efficiency below threshold". We have a mechanic we trust so we'll bring it to him this week. We spent a couple thousand fixing this car about two years ago and I'm not sure it is worth doing that again. Carmax offered us 1200 for it around this time 2012.
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99 Ford Ranger 4-cyl. Check engine light is on; pulled fault code: "catalyst efficiency below threshold, bank 1." Cat converter is new as is rest of exhaust, o2 sensors are new, and its been recently tuned 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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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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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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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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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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It says warm up catalyst below threshold (bank 2). Is this just an o2? and is it upstream or downstream if it is? When I scan other cars at work it normally says system is too lean/rich for o2's.
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P0420 bank 1 code popped up while driving. Im thinking this is just an oxygen sensor? Is it ok to drive with this code for a while if i buy an o2 sensor online?
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