Re: 2zz P420 - Lucky me :(

[dcod]

Hi,

Just been 'blessed' with a new CEL code - P420 (Catalyst System Efficiency Below Threshold (Bank 1)). My cat is a sports cat (6 months old) and I've just passed an MOT with decent emmisions.

I've read this "the efficiency of the catalytic converter and/or exhaust pipe and/or O2 sensor is not so great". Is this a good description? ie. it's your cat, exhaust or o2 sensor.

Any suggestions about or experience with this code would be great.

Thanks,

Dave

[Wabbitkilla]

Another one, this has been discussed recently in connection with a turbo.
Basically the sports cats aren't as efficient as the standard cat in keeping heated.
It only has to drop below threshold a couple of times for the code to come up and the weather is turning colder.

Simplest way of overcoming this is to fit an extender to the third O2 sensor.

[dcod]

Thanks, I read that thread, seems the only one that really discusses the code.

Just read this though on a ToyotaNation thread:

"My03 started pushing the code about a year ago. Got the same response from the techs as you. However, the light went out when I spent a week in Florida last July driving on Florida gasoline. Drove home on FL gas, no light. Fill up with Tennessee gas, CEL is on 16 miles later. It aint the cat, it's the ethanol blended gasoline. I suspect the programming genius did not take into account the possibility of the usage of ethanol blended fuel and thus the P0420. I have Honda throwing same code. I employed this fix on both vehicles and no light.
Go to this link:  m http://www.honda-tech.com/showthread.php?t=2162522 m . Follow it exactly and you have a good chance of ridding yourself of the P0420 CEL and saving yourself enough money to go for a nice vacation."

Coincidence has it that i've recently filled up with Total Excellium Super Unleaded to see what difference it has on my engine. It's been said a number of times that the 2zz should be run on 91 RON fuel minimum (regular unleaded). Just read that Excellium is 97 RON!

Could this have caused it? Havn't read the permanent fix talked about as yet.

[Wabbitkilla]

Ooh, that's a quirk I hadn't thought of!
Luckily I have an Apexi PFC on my car which gets rid of the third O2 sensor.
I've tried Excellium and the car runs nicely, I suppose a cat could behave differently with a different fuel formula especially if the formulation reduces the temperature of the burn.

[dcod]

Luckily I have an Apexi PFC on my car which gets rid of the third O2 sensor.

I wanted to do that but was trying to kep costs down  s:( s:(

Six months with nothing then the warning light 50mls into using high octane fuel seems quite a coincidence. Maybe if I reset the ECU it will adjust to the different values it's getting.

[Wabbitkilla]

Always worth a try resetting the ecu   s:D s:D  

Kind of reminds me of The IT Croud ... "Have you tried switching it off and on again?"

[dcod]

Kind of reminds me of The IT Croud ... "Have you tried switching it off and on again?"

  s:lol: :lol: s:lol:  I work with computers ... unfortunately, it's so true! (includes phones, routers, ECUs ...)

[markiii]

don't beleive the celica has a 3rd 02? are you running with a stock celica ecu for the 2zz?

[dcod]

Yeah, Celica GTS 2zz and ECU. Everything else is not stock Celica.

Is this the baby?



Now reset the ECU. Done about 20ish miles since the P420. Just a matter of waiting to see if comes on again I guess.

Question: Over what sort of time period can you have three P420's until it is flagged up? My exhaust/manifold has always created a lot of pops and bangs (letting off the accelerator and changing gear at low revs) ever since the engine was installed (5 months). Could these have created 3 P420's over a long period of time?

[markiii]

from memory the celica only has 1 02 sensor in the manifold and none post cat

is it wired up properly?

[dcod]

from memory the celica only has 1 02 sensor in the manifold and none post cat

is it wired up properly?

How does the Celica setup check the cat?

I believe Rogue know what they are doing but there's no harm in checking. Off to Google, don't wait up ...

[markiii]

not all cars check the cat functionality, mrs jap import is another example with no 02 post cat

[dcod]

Ok, from these 2 links, it appears there is 1 pre cat and 1 post cat.

 m http://www.newcelica.org/forums/showthread.php?t=135889 m

 m http://wiki.answers.com/Q/How_many_oxyg ... Celica_GTS m

I now have the question, why do I have 2 pre cat?   s:? :? s:?

[Wabbitkilla]

Ok, from these 2 links, it appears there is 1 pre cat and 1 post cat.

 m http://www.newcelica.org/forums/showthread.php?t=135889 m

 m http://wiki.answers.com/Q/How_many_oxyg ... Celica_GTS m

I now have the question, why do I have 2 pre cat?   s:? :? s:?

Darned good question.
The standard 2 has 2 precat, for bank1 & bank2, my guessing is that the 2ZZ swap manifold has both positions too - just how they're wired up is something only Rogue can tell you.

[markiii]

a question for rogue I'm afraid, I don't knw how/why Patrick chooses to wire it the way he does

[markiii]

actually from memory Patrick uses the standard roadster manifold with a new flange (never understood why as one set of ports is oval and the other round)

however, that leaves 2 precat chambers which will have half of the exhaust gas each.

I assume that he needs to sum the output somewhere/somehow in order to feed a single signal back to the Celica ECU whih is expecting a single sensor

[dcod]

Thanks for your help and replies.

My manifold is from ebay with the Celica flange welded on ... as far as I remember.



Just checking to see if a 2004 Celica GTS is any different as those other 2 links are about a 2000 GTS.

[dcod]

It appears that the Celica GTS pre cat sensor is in the mid pipe (between the exhaust manifold and the cat, under the car). So you are correct, they all seem to have only 2 (1 pre and 1 post cat).

I may ask Rogue how they wired in 2 pre cat sensors.

Would a pinout of the GTS ECU show that it can handle 2 pre-cat sensors? Does the pinout of the 1zz show that? Unfortunately, I can't find either at the mo.

[markiii]

It appears that the Celica GTS pre cat sensor is in the mid pipe (between the exhaust manifold and the cat, under the car). So you are correct, they all seem to have only 2 (1 pre and 1 post cat).

I may ask Rogue how they wired in 2 pre cat sensors.

Would a pinout of the GTS ECU show that it can handle 2 pre-cat sensors? Does the pinout of the 1zz show that? Unfortunately, I can't find either at the mo.

celica ecu can't handle 2 pre-cat sensors, pin outs in the library

[dcod]

celica ecu can't handle 2 pre-cat sensors, pin outs in the library

Thanks. Always thought I should have spent more time in the library than on the streets ...

[andywood]

Out of interest have you noticed when the MIL comes on (in terms of driving style etc..)?

I am pretty sure that the p0420 is on a 3-trip logic, but not sure if that has to be 3 consecutive cold-hot drive cycles though. Also not sure exactly what drive-cycle is required to complete the cat efficiency check but I would guess that it is combination of urban and motorway style driving.

I have found it hard to work out the root cause of my issue without knowing all the entry and trigger conditions for the diagnostic, but that is all probably buried at the bottom of a filing cabinet in Toyota HQ now!

Interesting to hear that you have a lot of popping/banging on overrun, could be a sign of things being a little too rich under certain conditions and 'flooding' the exhaust/CAT/o2 sensors with HCs that the sports CAT just can't deal with in time to avoid pre/post sensors seeing a similar change....

Although you are NA with different engine it is possible that we are both seeing the same issue, I am not completely convinced yet that mine is just down to sports CAT sensitivity, but would be very happy to be proven wrong! With no other codes/symptoms being flagged then i don't think it is too much to worry about.

Andy

[mrzwei]

Interesting to hear that you have a lot of popping/banging on overrun

Bit of a drift really but I had a new exhaust fitted to our camper van last month and then did 1500 miles in Europe. The popping and banging on overrun or when changing down, even at low speeds, was like a machine gun, embarrassing when driving through towns etc.

Took it back to the garage and they said air was getting back into the system. (could be  sbollocks bollocks sbollocks  really, more likely the dynamics of the new box which are different from the original).

They are fitting a new back box on Thursday which is a different design so I'll wait and see.

[Cap]

Dcod..

Your Exhaust Manifold is Manufactured to Look like a 1ZZ Exhaust System..  and Should actually have the Bolt Holes to hold the 1ZZ Heat Shields..  some Governments get funny about engine changes..  and this exhaust system will keep them from looking deeper into the engine compartment..  

When a 2ZZ Swap is done, the Right Side O2 Sensor on the Engine, is the Only One actually used..  the Left Side, just fills up the Holes, and looks Pretty for the Government Inspectors..  You can pull the Electrical Plug for the Left Side and have no ill effects..  

The 420 Code is tossed when the Rich/ Lean wave form Frequency reaches a certain Frequency..  As the ECU is fueling the Engine, the Air Fuel Ratio is being forced to Swing above then Below the 14.7 AFR Mark..  

You can see the 'Wavy Pink Line' on this Chart..  that is the AFR of a Steady Run down the Road..  The Brown Line behind it is the AFR after the Main Cat..  

[Second and Third lines ]



The 'Dithering' has the Function of Loading up the Cat Converter with O2 when the Fuel Ratio is on the Lean Swing ( Going Up ), then when the AFR's go below the 14.7 Mark, they are loading up the Cat Converter with Fuel..  

This Constant Swing has a Frequency that is Monitored by the ECU, and it will look at the After Cat Sensor to watch it's AFR Swing Also..  ( It Also has a Period, that is Slower, and not as pronounced in amplitude )..

As the Converter Ages, the Frequency of this Waveform Increases. When this Period gets to a 'Value' as programmed by the Wizards in japan, then a 420 code is tossed..  

When Oxygen enriched Petrol is used, then the Period of the Cat Waveform slows down..  and the Cell is Averted..  


Here is a Chart where the 'Dithering' has been smoothed by software ( Averaged ) ..  The Pink Line is still the AFR's but Smoothed..  and the Brown Line is the AFR's taken after the Cat with a Wideband Sensor..  

[ Second and third Lines ]


You will also notice the AFR's do not 'Overlay'..  as the Two O2 Sensors ( Both LC-1's ) were not calibrated at the Same time..  but are withinn .3 or so of each other..  Close enough for me..

Another 'Fix' for the Dreaded 420 code involves adding a Capicator and resistor to the O2 Sensor feed line to the ECU..  this will have the Effect of slowing down the Waveform ( Low Pass Filter ), and the Results are the Same..  No Cell..  If the Wiring is done at the ECU, then the Government Inspectors have to tear the Car Apart to find it..  so it's cleaner looking that the 'Anti-Fowlers' trick..  

Another way is to use a Wide Band O2 Sensor ( Like I Did ) and use it's analog Output to drive the ECU's Circuit.. and Before you install the Wideband Sensor..  Program the Output to be Time Averaged..  this has the Same Effect as Adding the Low Pass Filter..

This After Cat Install of the Wide Band went VERY smoothly..  and I was able to power it from the O2 Sensor Plug..  Just a Few Hiccups on the Power Issue, but I was ultimately able to Make the ECU happy to let me share the 12 Power for my LC-1 Controls.. and it thinks is Powering a standard O2 Sensor..  and it's all Plug and Play..  No Wire Cutting..  

This is a Shot of the 'Quick and Dirty' Install..  


Here is the Thread on Newcelica about the Resistor and Cap Method..  

 m http://www.newcelica.org/forums/showthread.php?t=216641 m

The thread gets off onto some Bad Information..  then later on an EE Comes in and sets the Record Straight..
Cap

[Ilogik]

Pretty sure mine is wired up with two pre cat sensors, they are in different positions  to dcods.  Will take ampeek at lunch time.

[markiii]

caps post can't be correct in this instance or the 02 in teh manifold would only be reading gasses from 2 cylinders