Question about 2001 Nissan Altima

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My friend has 2004kia spectra 2.0 with new sparkplugs and o2 sensor. service engine light still comes on and reads p0420. the top attached cat conv looks in good shape but comp reads cat inefficient. have heard that kia has problems with cracks in exhaust manifolds which is attached to top cat, can cracks cause cat reading to show bad converter ??

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  • Nissan Master
  • 3,951 Answers

Yes

Posted on Oct 13, 2017

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6 Suggested Answers

6ya6ya

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Posted on Jan 02, 2017

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GasparMacari

GasparMacari

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SOURCE: 1993 Nissan 300ZX idles high 1800rpm cold or hot.

yes, thats the typical symptom of a IAC valve giving you trouble, try cleaning it up but ull probabbly will have to replace it
have fun
hope this helps

Posted on Nov 11, 2009

Anonymous

  • 1 Answer

SOURCE: PO420 DTC code on 02 Nissan 2.5 Altima

i found out the cat bein broken up and suckin into the fudgin pinstons....good luck everyone

Posted on Feb 04, 2010

Anonymous

  • 39 Answers

SOURCE: PO420 code-service engine light is on

also check the cat by removing the o2 sensor befor the cat and look in the hole. if there is any deformity to the cat ( melted, holes, missing) replace it right away the nature of the 2.5l it sucks the cat matirial back into the motor damaging the rings and bearings. the most comon cause of cat failure on that modle is head gasket failure so before sinking 750$ in a cat have the head gasket checked.

Posted on Mar 29, 2010

carl

  • 3640 Answers

SOURCE: check engine light on

Diagnostic code produces P0420 catalyst system efficiency below threshold-Bank 1. Probable causes are listed as follows:
1-air leak in exhaust before rear 02 sensor, 3-Fuel system fault,
4-faulty catalytic converter.

Posted on May 31, 2010

localwonder

Michael Masters

  • 6784 Answers

SOURCE: Check engine light is on. Code reads p0420? Is

HI. This is a sign of a catalytic converter that is not working as efficiently as it should be. It is part of the vehicle emissions system. The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream O2 sensor waveform readings should fluctuate, but the downstream O2 sensor reading should be fairly steady. If the PCM detects that the two O2 sensors are reading in a similar manner, the DTC code P0420 will be issued. The necessary action are to check for any exhaust leaks at the manifold, pipes and catalytic converter. You will also need to check the spark timing to insure that it is normal and inspect the coolant temp sensor for its integrity. If all the check points test out ok, the remaining actions will be to replace your catalytic converter. A lot of the emission parts are covered under the warranty package if the vehicle is not out of its warranty contract. If you still have full warranty coverage at this time, this repair should be covered. I would check that out before purchasing any parts.

  • NOTE_ This code could also be triggered by using a leaded fuel in the vehicle. Make sure you are using the correct fuel blend. I should also point out that this is not a sensor issue. Your sensor(s) are actually functioning as designed. If they were not, you would not have this code. With that said; it wouldn't hurt to test them, if possible.

Posted on Aug 24, 2010

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2 Answers

Where is the O2sensor bank 1 at with a code of P0420. AND do I need to replace both sensors upstream and down. Or just the one that is showing up on the obd scanner.


Bank one is front side of cat. It should also tell u if it's cat 1 or cat 2. Depending on make an modle an yr. Catalyst 1 bank 2 is left cat back sensor. Catalyst 2 bank 2 is right cat back sensor. U do not have to replace upstream also. My o2 sensor Catalyst 2 bank 2 went bad. Had engine code for burning rich bank 2. Replaced tha down stream sensor an fixed problem runs better an better gas. This was in 97 gmc suburban. Idk what vehicle ur askin about. An I'm not to familiar with much about cars jus trucks an suvs.

Jan 02, 2017 | Cars & Trucks

1 Answer

04 Altima 2.5 s w 150k changed cat 2014 1 yr later p0420 code again what r normal reads for 02 sensors? reads @ idle fluctuate @ .3V b1 sensor & .8V b2 sensor.anyone had p0420 that wasnt a bad cat


Those cars are notorious for engine problems unfortunately. The exhaust valves tend to warp from heat after around 200k miles. Therefore throwing the O2 codes. Best outcome and cost effective thing I can recommend is replacing the engine with a new or low mileage engine.

Feb 18, 2015 | Cars & Trucks

1 Answer

I have a 2003 saturn ion 4 door, it has a ton of miles 194k. Last week the alternator went out do I replaced it without a problem, then the day after the check engine light came on I hook up the diagnostic...


p0420

no FSM> and not looking up P0420?
no engine stated, so ill get it wrong too..?????????????
420 is cat monitor failure. "efficiency"
the most hard of all.

ill make a list from hard and expensive .
1: bad sensor 2 rear. you failed to do both, that was WRONG.
2: bad cat. (i can weld on any cat for $99 bucks.) i do it last.. dead last.
3: engine running real bad. BUY a scan tool, now.

so the o2 is new that leaves #2 or #3.
i never shot gun cats. but shops do, its not their cash, huh?

i connect a real scan tool (not one that misses factory DTC codes)
then look at pendings for P042o , see funny sensor readings there, bingo.
i check every PID. for all sensors to be sure they READ right.
ECT AT 180F+ AND HOLDING? HOT.>?,
is the engine holding closed loop status at idle, no fix that NOW.
is LTFT (long term fuel trim ) near 0 or at - 40 or + 40% (fix that next)
if trim is good, the engine.
If the front 02 is new, the AFR will be correct and the the front 02 will swing fast and the trim will be near 0 , -4 is near best.
tad rich , natural.
once the engine is running Stoich at light flat cruise. (close loop) the
cat will heal its self (bake dry) and stop throwing 420. ( a hope deal)
if not the cat is bad.

ive cured some of the most hard 420s,.

on some ratty engines, a new cat can in fact hide it , until it cooks to death and next year 420 are back.
id never do that because gas is expensive. fix engine first.

Jun 24, 2014 | Cars & Trucks

1 Answer

What can i do to solve problem code p0420 on the car.


This code can be a pain... unfortunately P0420 means it could be several things. Depending on how old the car is...
- Check for exhaust leaks in all pipes and exhaust manifold (visual inspection, listen for that ******* noise evident of holes)
- Get an O2 sensor socket, remove the sensors and inspect. Peer inside the catalytic converter from top and bottom, look for clean horizontal honey comb pattern. Should be obvious if pieces are falling out. Look at O2 sensors for corrosion or fading of metal, they only last ~100K. Only the upstream sensor affects how the car drives though, the bottom one just measures how good the cat is doing. Either one can trip the check engine light though.
* Symptoms of driving performance may take awhile to develop, and either a bad sensor or bad cat can cause it to run rich and burn excess fuel. Running long times with a bad upstream sensor can lead to damage on the cat, so do the cheap O2 sensor replacement first.
[My 1998 civic had the light on since I got it in May, finally performance and fuel economy started dropping. Before buying an O2 sensor or new cat, I visually inspected everything and finally took the sensors out to look at them and inside the cat. The cat and bottom sensor looked okay, but the top was corroded (I figured it was the top since my driving was being affected). I replaced the top O2 sensor and she runs nicely now, I expect fuel economy to return. You can clean sensors sometimes (no water), but usually its corroded so just replace it. $70 for a sensor is WAY cheaper than paying someone to replace you cat, which is a recommended change if you end up having to get a new cat anyway (don't want to ruin a new cat with a bad sensor dumping fuel in).

Sep 08, 2012 | 2003 Pontiac Vibe

1 Answer

I have a P0420 code happening on my kia.What does that mean?


Code P0420 is a code for Catalyst efficiency. The computer is seeing the post Catalytic converter o2 sensor having too much activity. The Cat. should be cleaning the exaust of Hc, co, and Nox. The post cat o2 will read the o2 content in the exhaust and if it moves up and down too much or to high and low, the computer interperates that as the cat not ridding the exhaust of it's pollutants. This indicates that the converter is unable to preform properly. The problem could be a bad cat, o2 sensor (Pre- and/or post cat)or o2 sensor wires, or an air fuel mixture problem that has caused the cat to fail. Many other engine operating system failures can cause the converter to not work properly
hope this helps

Apr 03, 2011 | 2002 Kia Spectra

1 Answer

Code reading p0420 on '99 chevy s10 blazer, low catalyst threshold. Is this a bad catalytic converter or burned valves?


there are a couple of things to consider here. That code indicates that the O2 sensor behind the cat is not functioning like the engine computer expects-either the cat itself is not functioning properly or you may have an exhaust leak, or the heater circuit in the O2 sensor is faulty. The cat should get up to 600 degrees and it burns unburned fuel before ti gets to the 2ed O2 sensor-if it cannot do this, the CEL comes on and you have a P0420. Before replacing the cat, clear the code and see if it comes back-if it does, you might try first replacing the O2 sensor. If that doesn't work, get a 'oil fouler' spark plug adapter and install the O2 sensor in it, then install both into the exhaust-this 'shields' the tip of the O2 sensor and slows it down, fooling the engine computer into seeing it switching slowly, as it is supposed to do. Your only other choice is to replace the cat, and an aftermarket cat is much less than an OEM unit.

By the way, if you have burnt valves, a P0420 is the least of your worries.

Apr 01, 2011 | 1999 Chevrolet Blazer

1 Answer

I have a 2002 Chevy S-10 Crew cab 4wd LS. I was


p0420 is Catalyst System Efficiency Below Threshold (Bank 1) o2 sensors reading are used to check the cat if the cat is plugged you will lose power o2 sensor send a voltage signal to the computer 0 to 1 volts The o2 upstream of the cat should switch back and forth from 0 to 1 volts, average .450v if voltage stays high engine is running rich (low oxygen) if voltage stays low engine is lean (lots of oxygen) cats have a 8-year 80000-mile warranty

Jul 11, 2010 | 2002 Chevrolet S-10

2 Answers

Trouble codes


You mean P0420? You need a new cat converter. The "Mechanic" couldnt tell you that?

Nov 25, 2009 | 1998 Chevrolet Venture Cargo

1 Answer

Engine light codes 02-3151 and P0420


Code P0420 is a code for Catalyst efficiency. The computer is seeing the post Catalytic converter o2 sensor having too much activity. The Cat. should be cleaning the exaust of Hc, co, and Nox. The post cat o2 will read the o2 content in the exhaust and if it moves up and down too much or to high and low, the computer interperates that as the cat not ridding the exhaust of it's pollutants. This indicates that the converter is unable to preform properly. The problem could be a bad cat, o2 sensor (Pre- and/or post cat)or o2 sensor wires, or an air fuel mixture problem that has caused the cat to fail. Many other engine operating system failures can cause the converter to not work properly.

Sep 10, 2009 | 2000 Toyota Corolla

2 Answers

01 toyota tundra stalls at idle....engine code p0420


Could be a problem with the Catalytic Converter or oxygen sensor (H02S bank 2 )

Sep 09, 2009 | 2001 Toyota Tundra

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