Subaru - Outback :: Intermittent Check Engine / Code PO420 - Catalyst System Efficiency
Feb 2, 2014
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 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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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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Got this engine code error, how to proceed?
I have a '00 accent, just purchased a few days ago from a private party, when I bought it, I had a mechanic look it over, gave me the OK and said it passed inspection, no mechanical or obvious running problems with the car.
So I was driving around yesterday and the check engine light came on, took it to get the oil changed because I wasn't sure last time it was done, had the oil changed, light stayed on.
So I took it to auto zone to read the error code, was given this information. How to proceed?
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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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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 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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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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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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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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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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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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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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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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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 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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I purchased a 2001 Subaru Forester about 4 years ago. Within 48 hours of buying it from a dealer, the check engine light came on showing the PO420 code. The car was running fine without any problems and it was suggested to us by 2 independent mechanics that Subaru is notorious for throwing this code, so we didn't investigate it any farther besides doing a fuel system clean/flush that was offered to us by the dealer.
Lately, the car has started sort of shuddering during acceleration so we figure it's time to look into this more, but just trying to figure out where to start. From what I understand, this model has 2 catalytic converters and 2-3 O2 sensors. I've been reading as much as I can on the topic and watching videos trying to figure out our options and whether we should try replacing the O2 sensors first or just go for replacing the whole shebang. I know we cannot afford the pricey repair of it all right now so the car will have to sit for quite some time before we can do that; however, if we can figure out how to do it ourselves, we could get it done much sooner.
My questions are:What is the likelihood that this could still be an O2 sensor issue considering the shuddering when accelerating?
What other signs do I look for besides rattling in the cats to know they might be bad?
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I have a 2006 F-150 with the 5.4L. I got the check engine light and the computer says catalyst deficiency bank 2. So I assume the passenger side converter is blocked. Is there anyway to either take out the cat and replace with a piece of straight pipe and bypass the o2 sensors or take the cat out of the housing and put the housing in and then bypass the o2 sensors.
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What are reason for the check engine light to come on and off and when a different person drives it. When it comes on? I guess I am looking for other opinions when I drive it I drive it respectfully but the owner bit of a speed lover.
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