Dreaded P0420 Code

[roks]

For a month or so I've been driving with the engine light on, it happened once before and disappeared by itself. I got one those bluetooth obd2 scanner and reset the light. Now I see the 'Pending 0420' code.

Please can some one tell me if the o2 sensor are ok from this graph. I hope I plotted it correctly, used Torque Pro, still getting used to it.

It appears the when at a stop or idle sensor 2 is oscillating instead of stead reading, seem to OK when o the go.

Is it the sensors or am I going to have to fork out fore a catalytic converter?

[Normanc Cook]

Hi Roks,

I have a similar problem and have just posted a similar topic.

I have read elsewhere that there was a software update that widened the parameters for the post cat sensors as this is a fault in the original programming. Don't know if you have come across this? I did wonder if the same thing could be done by fitting resistors inline from the lambda sensors to reduce the voltage going back to the ECU, thereby preventing the bogus P0420 and P0430 faults.

Let me know if you come up with a solution!

[roks]

Normanc,

I have managed to get rid of the P0420 code after a lot of head scratching. I know for sure that if I had taken it to the dealer or a garage there would have been whole lot of guessing work.

After crawling the web, I realised that it may not be the CAT or the sensors that's actually faulty, rather just dirty. I do a lot of local driving, and I tend to change to high gear a lot and my mileage per gallon was 28.

This is what I did to burn off the gunk (or at least I think it did) on the O2 sensors/CAT:

I reset the code with Torque on my phone.

Filled up the tank with Shell V-Power and took it for a spin on the motorway to get the cat and o2 sensor in a 'ready' state.

Couple more tank of Shell V-Power - drove in lowest gear possible to keep rev up.

Then checked for the code again, it now came up as 'Pending' P0420.

Then went on a weekend trip (380 miles), Shell V-Power again, checked the code and its gone.

That same weekend trip 6 months ago consumed one and quarter tank. This time around I had quarter tank left, although the oil change may have helped as well. Mileage per gallon 38.9 and climbing.

On the attached pdf, page 12 it tells you how to get the cat/o2 in ready state after resetting the code.

I hope it helps you in some way.

READINESS_MONITOR_DRIVE_PATTERNS_T-EG02-003.pdf

[oldcodger]

Hi,

Was just reading an article in AutoExpress about Halfords who are saying if a car they test fails the MOT emissions test, the owner can buy a can of Cat A Clean from them, and if it does not pass the emissions test after that then Halfords will refund the cost of the Cat A Clean.

Used it some years ago on my dodgy Avensis and it got though with results better than the year before !

[roks]

Forgot to mention that my corolla pass MOT, the emissions test with flying colours, readings were slightly lower than last one.

[chaza]

take it to a good Toyota Dealer... not that expensive... job done....

[roks]

Had the P0420 again about three weeks ago.

It came on couple of miles after I fill up the first tank of winter fuel, apparently winter fuel has more butane to stop gelling. Did some high rev driving for couple of weeks, didn't go away so I reset the code.

Just did a 360 mile round trip on a full tank of Shell v-power, is that good mileage for a full tank?

Do o2 sensors have a service intervals or do you replace when they go faulty?

Is there a way to test the CAT?

Thanks

[mcorban]

Looking at your graph, Bank 1 sensor 1 should switch like that, as it is reading the emissions, and adjusting fueling to suit.

Bank 1 Sensor 2 on the other hand should be a lot more uniform.

I went through this with a corolla, and changed sensors to no avail.

An emissions test should indicate.

The sensors are pretty robust. Is your car burning oil?

If its not a sensor fault, it s most likely a cat fault.

Generally, but not always once the post cat sensor reading (B1S2) is similar to the precat (B1S1), it would be indicitive of Cat failure.

A Precat sensor fault would create a poor running engine, and perhaps down on power

[roks]

Hi Mike,

After 6 months, the dip stick showed middle of the min-max mark, so I topped up 0.5L, I would think this is normal no?

Car seems to running OK.

I got a bottle of CATACLEAN, but I am bit sceptical about poring it in and making it worse.

[oldcodger]

Mine uses about .5 to .75ltr with 12K miles in a year, how many miles have you done for your .5ltr of oil.

Re you previous entry, some folk say you can take out and clean you o2 sensors but believe generally you are more likely to damage them even more.

Using the Cataclean should be all you need, just follow the instructions on the can.

Do you think Halfords would use it if there was a risk of damaging customers engines !

Sensors / Error codes can be problematic, my old avensis would put up a code for 20 mins then it would go off on its own, sometimes returning next day or next month !

Would replace one or both before replacing the CAT unless it was specifically diagnosed as the fault.

If you do buy sensors buy genuine totoya ones, as was metioned in this post, as buying third party sensors can lead to even more problems.

http://www.toyotaownersclub.com/forums/topic/165287-car-mechanics-16-corolla-electronics-diagnostics/

[roks]

Hi Oldcodger,

I've done just over 2k miles since the last oil change in June. I've also tightened the 2 centre bolts a bit so plug wells are dry but still some weeps behind engine. I got the gasket but waiting for better weather to do the job I guess.

I don't think I'll bother with the cleaning o2 sensor. Also, I am not sure if they are the original, I have not had a closer look but sensor1 looks quite clean appearance and cable very short, not sure if its supposed to be stretched like that.

I'll chuck in the cataclean and see if I get different reading on sensor 2. And when you say genuine Toyota, are they Denso ones? And can I buy from anywhere long as its denso part number?

[mcorban]

I used genuine but have used Bosch ones before with no issues.

I would try the denso ones as they are oe. The reading on your bank 1 sensor 1 looks pretty good. The cable is quite short but shouldn't be stretched. If it is faulty it can cause misfiring and other symptoms.

Catclean would be the way to go, but an emissions test would nail it down.

The fact that your not burning too much oil is a positive.

Perhaps you might have your last reading from your MOT, it might give you an indication.

I used a direct fit CAT and it is doing the business two years on

[oldcodger]

Yes, that front sensor should have some slack on it, say an inch or two , on mine there is a wire hook from the rocker cover going over to hold the sensors cable up and away from the hot exhaust,

Would suspect your sensor may not be the right type if its cable is so short - prehaps the root of your troubles ?

You may find a genuine sensor from toyota is stamped Bosch or denso, usually motor factors like andrew page will also stock them at a much lower price, and you should be ok with them, but I would avoid any other brand /clones/ebays

If fitting a new rocker gasket be aware you need some silicone as well, see this thread / diagram

http://www.toyotaownersclub.com/forums/topic/165392-oil-leak-on-back-of-block/

[roks]

Thanks guys, I'll take a look at the cable again, perhaps there is an inch or two slack. I'll also try to see if the sensor is a stamp with anything.

I am hoping cataclean will smooth out the sensor2, its supposed to be flat' ish line but not sure at what voltage.

By the looks of it, it may be the original cat, but the rear silencer box looks a bit shiney in appearance so I guess its been replaced at some point.

[oldcodger]

Think you have two choices, either have the car properly diagnoised and repaired or Diy.

If its Diy think you ought to first ring your local Toyota dealer spares dept and get a price for both sensors.

Then try, say a branch of Andrew Pages who stock the BluePrint range of OE spares and see what prices and makes of sensors they stock.

Would not bother looking at anything else as you really must fit genuine parts or you could be running around in ciircles.

Also look at your exhuast, is there a clamp just behind the rear silencer where an after market one has been fitted ? ( original is oval shaped)

No expert on the exhaust system but the sensors, cat and boxes are all part of the same tuned system, if the rear silencer has been changed for a 'sportier' model, ie non standard, that could afftect the exhaust pressure and so the sensors etc.

[roks]

I am assuming someone changed the silencer box, because its less rusty looking than the rest of the pipes, it doesn't look like sports type.

By 'clamp' do you mean the bit where the silencer box is fitted to the exhaust pipe?

[mcorban]

If it's an original exhaust, the exhaust should run from the flange between the engine and cat right back to the rear silencer, with no joint. And if you are doing any exhaust repair, do not use any exhaust paste pre cat. Also beware they are quite heavy.

The rear box on my e11 is original and still shiney.

[roks]

Mine looks very similar to bottom one on the picture, 3zz-fe.

[mcorban]

Roks

I have read through some of your posts again.

This is only my experience, i had changed the engine (2006 corolla) as i knew it was shot, but prior to changing my cat i had both sensors put in (genuine) My car is older, but it was giving me 28-30 mpg (on board computer reading) prior to changing the cat.

Once i changed out the cat (an aftermarket direct fit repacement) it now averages 38-40 mpg, again on the on board computer.

I hope this may give you some insight.

One thing i will say, the replacement was a good quality replacement, and had the exact dimensions of the original.

I had tried a universal replacment, on the old engine but it lasted a week!

[roks]

I used a bottle of Cataclean about a month ago, I didn't notice any difference.

Have been using Shell V-Poweer petrol for few months, filled up today, went on 20 mile trip, check engine light came on. It was mixed, local traffic and dual carriage ways, speeds 10-55mph, freeze frame data below:

Freeze frame information:

-----------------------------------

Engine Load = 45.49%

Engine Coolant Temp. = 89 'C

Fuel Trim Bank 1 Short Term = 0%

Fuel Trim Bank 1 Long Term = 9.38%

Engine RPM = 2340.5 rpm

Speed (OBD) = 44.74 mph

Intake Air Temp. = 15 'C

Any thoughts?

Just to add, I've been drive mostly 'high gear as possible' for last few days and also I think when the light came on, I think I was changing to 4th/5th, thought I was driving over a small bump as I felt a tiny shake as I hit the gas.

I am thinking its my driving style that's caused the light to come on?

Thanks in advance.

[roks]

I am seeing a pattern here

I fill up at the petrol station, go on a motorway, drive 20-30min, hit bit of rough road surface, engine light comes on.p0420.