P0420 CEL 99 civic si

[preferredduck]

ok so let me give you the scoop on my car. its a 99 civic si with a jdm b16(2nd gen). i am running the stock si ecu and everything is wired up obd-2b, you wouldn't know there was a swap until checking the block code.

modds- intake, header, exhaust, aebs manifold, FPR, CTR cams, valves were adjusted a little tight for the cams
-new parts- distributor, cap, plugs and o2 sensors are a couple of years old.

ok a couple of years ago i would get a phanton CEL for the o2 sensor on the high bank, had a new one installed and still had the CEL. found out the person who did my swap had my timing at like 25 degrees BTDC, adjusted that to stock timing. later found out the Map sensor was plugged by a homemade gasket on the throttle body. got that fixed and no more CEL and stalling while driving down the road.

now over the past 3-4 mos i have been getting a CEL of the cat converter below threshhold. i checked out a few things and noticed my FPR was set where a d16y8 should be set at. so i set it to 48 which is on the high side of the b-series in the haynes manual. light went away for a couple of mos. then started to randomly come back on with no set pattern. checked the FPR and it was where it should be so i bumped it up abt 2psi, reset ecu and problem gone for 3 weeks. today the CEL came on for the same reason. FPR is still set correctly. i noticed in the past my CEL would come on when the a/c was running and the car was under a heavy load even a couple of mos ago, but the a/c wasn't on today at all and i have to use it when it rains.

i have not checked the timing as of yet, no misfires that i can hear and honestly the car has run way better of the last year than it has before(only after chasing an ase certified mechanics "ghosts"). Now i have noticed over the last couple of weeks that on first start up it runs a little rough for about 10 seconds when it was really cold. i know many things can cause these codes and have checked most of them out but i need to think outside the box on this one. is it possible that b/c of my mods running a stock usdm si ecu may cause a mis communication with the ecu and throw the code. i know when it was running very lean the CEL came on after 300 miles on the dot.

another observation, i had a small coolant leak on the upper hose and replaced it and thought i added enough coolant, well in the drive through the other day my car started to get hot, the fan kicked on and the temp raised but it stopped at a certain point and would not go any higher(no it was not even close to the red). so i checked the resevior tonight and it was below the minimum in the tank and could not see coolant in the radiator, i had read that low coolant can sometimed interfere with the ecu check on the car and cause this code. i will be filling it up with coolant in the am and checking the timing.

please any suggestions or ideas would be helpful b/c when the CEL come on my gas mileeage goes down and i would like my car to be in good running order. ask any questions you want and i will get the info if i do not already know. btw i have seen noo coolant leaks and have looked that over big time. If my cat is shot to shit i guess i will get a test pipe for now(no emmissions yet).

[jvillagran2000]

thats your catalytic converter if you have one take it down and inspect it,I've seen them break apart inside and clogg the exhaust pathway.

[BTEC]

get a cat and put ur fuel pressure back to where its supposed to be. 45psi with vac hose off is where it should b i think.

[preferredduck]

get a cat and put ur fuel pressure back to where its supposed to be. 45psi with vac hose off is where it should b i think.

haynes manual says 41-48 psi and since i have mods i took it to 48. after resetting the ecu and driving 20 miles the CEL came on again but it happened when going to redline, i had my g/f behind me checking for smoke etc and there was none. i think my FPR might be set like 2 psi higher than 48 which im about to bump down a couple of notches. i spoke with a trusted mechanic today and he seems to think it may be the sensor and i think i have 2 of those laying around to try. i'm just worried that my cat is fucked b/c of someone sabatoging my swap. it ran out of time and with 10psi too low on the FPR for a minute so i think it may be fouled. so how exactly can i check the cat without taking the damn thing off. like i said i had a phantom o2 sensor code a while back which led me down the trail of a mechanics screw up, and his reply was "bring it in it's 65/hr" thats when i realized he knew what he did. throttle screw was out of whack, timing, etc. but it's been running like a champ ever sinve the fist p0420 CEL. its just RTarded.

keep the ideas coming guys

[preferredduck]

thats your catalytic converter if you have one take it down and inspect it,I've seen them break apart inside and clogg the exhaust pathway.

i might just hollow it out and find a p30 ecu even though i should have one, but thanks to the guy who did the swap i no longer own it"BASTARD"!!!!

[green91]

your fuel pressure won't set the cat code, this code is set entirely on the length of time your converter is able to store oxygen, which compares the signals of your b1s1 and b1s2 oxygen sensors. however, running incorrect type and fuel pressures will make your EGTs out of an acceptable range and will damage your cat converter much faster than a normally functioning engine. most cats only have a 80-120k life expectancy.

[preferredduck]

your fuel pressure won't set the cat code, this code is set entirely on the length of time your converter is able to store oxygen, which compares the signals of your b1s1 and b1s2 oxygen sensors. however, running incorrect type and fuel pressures will make your EGTs out of an acceptable range and will damage your cat converter much faster than a normally functioning engine. most cats only have a 80-120k life expectancy.

damn mine is at 180k miles. but as i have read the cat does not gradually go bad it just goes. it ran lean until i found out what the mechanic did and i know that will mess up a cat, and it does it randomly where if the cat was gone it would be a constant thing correct.

[singhondeck]

i hav a 99 altima..i have the same code..i put in my header and the precat got removed...but the problems comi from my o2 sensor..basically its not readin the way its suppose to and is gettin too hot..so i need some type of spacer which brings it out a lil frm the downpipe

[singhondeck]

thats your catalytic converter if you have one take it down and inspect it,I've seen them break apart inside and clogg the exhaust pathway.

sometimes the pices get sucked into the engine..then ure fucked

[green91]

damn mine is at 180k miles. but as i have read the cat does not gradually go bad it just goes. it ran lean until i found out what the mechanic did and i know that will mess up a cat, and it does it randomly where if the cat was gone it would be a constant thing correct.

I'd say your car has a very lax monitoring strategy for the CAT then. They do gradually go bad over time. The CEL comes on when the catalytic converter's efficiency actually is less than a determined value in the computer. So they can be gradually going bad, but not set the CEL until its to a certain point.

Cat converters are usually a 2-trip logic detection code. Meaning it takes 2 complete drive cycles to run the monitor to check to see if the cat is good. Its possible yours on right on the borderline right now and at times just makes the mark and sometimes come up short. It probably won't hurt your car to drive with it like this, but it will get to a point where the CEL is constant.

[preferredduck]

I'd say your car has a very lax monitoring strategy for the CAT then. They do gradually go bad over time. The CEL comes on when the catalytic converter's efficiency actually is less than a determined value in the computer. So they can be gradually going bad, but not set the CEL until its to a certain point.

Cat converters are usually a 2-trip logic detection code. Meaning it takes 2 complete drive cycles to run the monitor to check to see if the cat is good. Its possible yours on right on the borderline right now and at times just makes the mark and sometimes come up short. It probably won't hurt your car to drive with it like this, but it will get to a point where the CEL is constant.

i don't want to risk screwing anything up. i have another O2 sensor im gonna put in but im also gonna pull the cat off and check it out. it was a constant CEL when the fuel pressure was low, but after that it went away for several months almost like the o2 code i used to throw, the sensor was good but the ecu couldn't figure out what was going on. i for some reason think im about t have to spend $$ i dont have to keep the car on the road and not eat up the premium gas i have to run.

[green91]

Unless its completely blown out, you can't look at a catalytic converter and tell if its bad. A fuel trim issue will set a completely different code.. usually a p0171 if its really lean.

[Tech5]

Unless its completely blown out, you can't look at a catalytic converter and tell if its bad. A fuel trim issue will set a completely different code.. usually a p0171 if its really lean.

Correct even a small hole that the human eye cant see can trigger this code

PO420 Means You need a cat, it will still run 100% but in order to pass emissons and get the light off you will need it replaced!

[Bruce Leroy]

spark plug defouler FTW...

There are so many threads being created about defoulers, it would be nice to compile everything into a single thread with the hopes that it could become a sticky. I will attempt to do so, addressing issues relevant to those using a race header.

Rationale for defoulers, this from Pro Street:
On ODB-II vehicles (96+), the ECU has two O2 sensors for diagnostic purposes. The first O2 sensor is located before the Catalytic Converter. This O2 sensor is responsible for all the Air/Fuel tuning and is imperative to the operation of the vehicle.

The second O2 sensor is located after the Catalytic Converter. The whole purpose of this O2 sensor is to ensure that there is a functioning catalytic converter in the system. The way it can detect this is to make sure that there is a difference in exhaust gasses between the first O2 sensor and the second. If the same exhaust reading is detected, then the ECU knows that there is either a damaged Catalytic Converter or no Catalytic Converter at all.

The ECU will then trigger a Check-Engine Light. On some instances, the vehicle will be thrown into a "Null" mode where the vehicle will not go over a certain speed and will be basically rendered useless.

This mechanical O2 fix is basically a way to space out the O2 sensor so that it still reads SOME exhaust gasses but it removes the O2 sensor from the direct flow of the gasses as to make the ECU believe there is a restriction in the exhaust gasses such as by a Catalyst.

From E46fanatics:
WHO: People who upgraded to aftermarket headers without installing any catalytic converter will get a catalytic inefficiency error code. Likewise, people who install high-flow catalytic converter will get the same "inefficiency" error codes.

WHAT: Catalytic Inefficiency codes on the post cat 0xygen sensor: P0420 (cylinder 1-3) P0422 (cylinder 4-6).
Ref: http://www.obd-codes.com/trouble_cod...old-bank-1.php

WHY: The reason why your OBD-II diagnostic systems report this error code is because the 02 sensors detect an above normal exhaust reading when compare to OEM catalytic converter. The OEM catalytic converter does an excellent job at filtering/cleaning/converting exhaust fumes into cleaner air. The DME/ECU calibrates its post-cat sensors to the OEM catalytic converter performance and specs. Therefore, aftermarket cats do not clean well enough to satisfy the catalytic efficiency monitoring of the DME. This is a very common problem with aftermarket cats especially the high-flow ones.
An "inefficiency" reading does not mean that your catalytic converter is broken especially if it is brand new. Again, the error codes just means that they are not performing as efficient enough to meet OEM standards.

SOLUTION: There are three feasible options to solve this inefficiency problem

Ignore.
Spark Plug non-fouler (aka Spark Plug defouler)
Software upgrade

-Ignore-Since the post catalytic converter oxygen sensors is purely for emission monitoring it does not in ANY way affect your fuel trim and car performance. Therefore, it is perfectly fine to ignore the check engine light.
-PRO: No time and resources wasted on fixing problem
-CON: Annoying check engine light

-Software Upgrade-Software upgrade from major tuning companies will flash your DME to remove the "catalytic efficiency" monitoring feature.
-PRO: Fast and requires no hardware/equipment modification to exhaust systems
-CON: Expensive

-Spark Plug non-fouler (aka Spark Plug defouler)-By installing the spark plug non-fouler, you are in essence moving the rear 02 sensor out of the direct flow of the exhaust stream/flow. By doing so, you are tricking the 02 sensor will an inaccurate reading. Since the 02 sensors is not directly in the path of the exhaust fumes, it can not accurate measure the exhaust fumes.
-PRO- Inexpensive
-CON- None

Types of defoulers:
1. Angled. As the name suggests, the defouler is angled at 90 degrees, which allows for greater clearance. This is especially important on Vibrant and BuddyClub headers.



2. Straight. These are straight, which seems fine with DCSports race headers, but not the Vibrant and Buddy Club.



DIY defoulers: There have been a number of threads about making your own defouler.

http://www.8thcivic.com/forums/bolt-...-defouler.html

solution: Check engine light w/ aftermarket Headers - E46Fanatics

Installation:



All defouler threads on 8th Gen:

http://www.8thcivic.com/forums/searc...archid=2352001

Where to buy:

eBay Motors: O2 sensor angle header WRX STI EVO 350z Civic SI tC RSX (item 250268957202 end time Jul-19-08 21:27:57 PDT)

This guy does stuff for VW's: [email protected] e-mail him with your request.

[email protected]

Mechanical 02 Simulators

A&J Racing :: Intake & Exhaust :: T1R O2 Fix

BLOX Racing Check Engine Light Eliminator - BLOX Exhaust Parts

Universal - Cel Eliminator 963-111-101 >> Weapon R Cel Eliminator

King Motorsports Unlimited, Inc.

Defcon Products : Oxygen Sensor Simulators

Hope this helps everyone out. We want this info to be disseminated to as many people as possible who either have race headers or are considering them.

Please post any extra info you have that would benefit fellow members here on the forum.

[Bruce Leroy]

Correct even a small hole that the human eye cant see can trigger this code

PO420 Means You need a cat, it will still run 100% but in order to pass emissons and get the light off you will need it replaced!

CORRECT.... I was replacing O2 sensors and other bs, Listening to my dads "Mechanic"... Trust the obdII

[preferredduck]

i ahd spoekn with my "good" mechanic today and he mentioned just to put a high flow cat on and a defouler so the CEL will go away, which is the cheapest thing to do. i have the DC 4-1 header on my car and was told years ago that that would eat up o2 sensors. i do not have emissions but im sure it will be here soon. i would hate to keep running it if the cat was blocked for some reason cuz them im looking at a bigger problem. there are 85k miles on my motor and my girlfriend said not a bit of smoke came out of the tailpipe running up to redline through 3rd gear, not even the typical honda black smoke. i'm gonna look at the cat tomorrow and see if i see anything, but i have always wanted a highflow cat or test pipe and the defouler would make it where i can run it correctly b/c i hat my CEL, it drains my gas.

[preferredduck]

look down

[preferredduck]

damn my computer may have spit a CEL for posting three times!!!

[preferredduck]

CORRECT.... I was replacing O2 sensors and other bs, Listening to my dads "Mechanic"... Trust the obdII

thanks for the breakdown b/c i don't like chasing sensors and b/c the car has been boosted, ran lean, out of time etc i think it's going bad but not there just yet, but when i sell my cylinder head thats what i'll get. the ebay link does not work but i found a few others for honda's

[preferredduck]

does anybody here know where i can sell my old cat and get decenst $$ for it, i know at one time they sold for a lot but not so much anymore. if i can sell the old one for abt what a high flow cat costs i can solve the problem shortly. if not it may take a while.

[Bruce Leroy]

If u dont have the $$$ just put the defoulers in your stock cat. THats what I did.