Advice please - Code P0420

[normanh]

The cars just thrown this code -catalyst efficiency below threshold bank 1. The car was pretty hot when it threw this yesterday after some 80 miles driving M25/M11/A11. Not seen this before so what's the cure/solution guys?

Norman

[MRSwede]

A quick google search

    Faulty oxygen sensor
    Faulty air-fuel sensor
    Worn or internally failing catalytic converter (Most Common)
    A leak in the exhaust system
    Misfire (the root cause of converter failure)
    Rich or Lean air-fuel ratio (the root cause of converter failure)
    Leaded Gasoline (the root cause of converter failure)

[1979scotte]

O2 sensor or Cat isn't it?

@Ardent
@shnazzle
@Carolyn

[Topdownman]

There is a thread here that may help;

https://www.mr2roc.org/forum/index.php?topic=67682.0

[Carolyn]

O2 sensor or Cat isn't it?

@Ardent
@shnazzle
@Carolyn

Yes it is - nine times out of ten - it's the cat, though the cat is less likely to be at fault when it's hot.

Either way it's a bit of a bugger- 'cos it's a 'replace the part and see what gives' scenario.

The original cats on these are getting long in the tooth and many of us have replaced the original with an aftermarket one from Cats2U. (The oem one costing a first born child and the national debt!)

So it's either £60 for a sensor or £135 for a cat plus crush ring gaskets.  If you're unlucky, you end up buying both.

[mr2garageswindon]

How about go to a friendly MOT station and ask if they can perform a cat emission test on it. The readings will help you make a more informed choice.
If the CO is high and the lambda reading is correct or close enough you know its the cat at fault..

[Tomo70]

First check the condition of the flexi's. It may that you have a leak on the system. You won't necessarily hear it blowing.
If you have an aftermarket pre cat with no support and a 12year old cat. The flexi's may have failed.

Then sensor checks.

[Dev]

 The cat below efficiency is a code that is only tripped when certain parameters are satisfied. I do not know them specifically but it is when the car has enough start and stop cycles and high way conditions where the temps are stabilized. If you reset the code it may not come back immediately and will usually come back on once those conditions are met again which can take a few days if you only do quick trips or will come on once you drive a good while on the highway. 
 I would reset the ECU and then observe how fast or how slow the CEL is illuminated. If it take a good while then its most certainly the catalyst that has to be replaced.
 

[normanh]

As far as I know the flexis were in great condition checked them out in the summer.
Reset the code this afternoon and had a brisk drive to get some Cataclean - thats been added to around 23 litres of fuel then drove home about 10 miles in total no repeat light on dash.
Back in September I mistakenly left off the oil filler cap the result was I sprayed just over a litre of very clean synthetic oil all over the engine including the manifold O2 leads could this cause the problem it was a bloody mess lucky its clean oil, could this have caused a bad connection on the cat socket?

Recheck the flexis, Cat Sensor first I guess then?  Its not burning excess fuel have done some 230 miles on just half a tank of fuel

Norman

[Ardent]

Nothing really to add other than in true ROC fashion. Let's start at the free/cheap end of the diagnosis pathway.

Edit.
If you have an obd dongle and torque Pro,  and look for the post cat senor info, that may also give a clue. Go for a drive and record  the sensor data.
Is it actually doing anything?

[normanh]

Just looked at the cat prices and we need a type approved cat cost 180 to 280 depending on make Cats2u prices.

Will run the car for a bit and see what happens now, will clean up the plugs and sockets of oil tomorrow if its dry.

Next would be Cat sensor then cat, chances are I might damage the the old sensor removing it so little point try to add to a new cat. What a bugger just as Essex is bordering on Tier 3 I need the fitter son's skills.

Norman

[Ardent]

@normanh

you have a PM

[Carolyn]

Just looked at the cat prices and we need a type approved cat cost 180 to 280 depending on make Cats2u prices.

Will run the car for a bit and see what happens now, will clean up the plugs and sockets of oil tomorrow if its dry.

Next would be Cat sensor then cat, chances are I might damage the the old sensor removing it so little point try to add to a new cat. What a bugger just as Essex is bordering on Tier 3 I need the fitter son's skills.

Norman

£120: plus you'll need gaskets.

https://www.ebay.co.uk/itm/TOYOTA-MR2-ROADSTER-CATALYTIC-CONVERTER-CAT-1-8-VVTi-03-00-02-01-FITTING-KIT/130353313042?fits=Model%3AMR+2&epid=2065675609&hash=item1e59a9b512:g:M8MAAMXQ1PNRZbGg

[normanh]

https://www.ebay.co.uk/itm/TOYOTA-MR2-ROADSTER-CATALYTIC-CONVERTER-CAT-1-8-VVTi-03-00-02-01-FITTING-KIT/130353313042?fits=Model%3AMR+2&epid=2065675609&hash=item1e59a9b512:g:M8MAAMXQ1PNRZbGg

Thats not type approved Caroline and should only be fitted to cars pre Feb 2001 mines later 2001 and comes in at from 180 plus post but includes the bolts and gaskets crush rings for the manifold end and wire cone to the exhaust. I checked with Cats4U earlier.

Norman

[Carolyn]

https://www.ebay.co.uk/itm/TOYOTA-MR2-ROADSTER-CATALYTIC-CONVERTER-CAT-1-8-VVTi-03-00-02-01-FITTING-KIT/130353313042?fits=Model%3AMR+2&epid=2065675609&hash=item1e59a9b512:g:M8MAAMXQ1PNRZbGg

Thats not type approved Caroline and should only be fitted to cars pre Feb 2001 mines later 2001 and comes in at from 180 plus post but includes the bolts and gaskets crush rings for the manifold end and wire cone to the exhaust. I checked with Cats4U earlier.

Norman

They are ALL the same, honest.  Don't believe all the listings.  The 'type approval' is a certificate that comes with it.. many members on here have fitted this item, regardless of model year.  No tester ever asks for the certificate.

But so long as you're happy.

ps My name is Carolyn...

[1979scotte]

https://www.ebay.co.uk/itm/TOYOTA-MR2-ROADSTER-CATALYTIC-CONVERTER-CAT-1-8-VVTi-03-00-02-01-FITTING-KIT/130353313042?fits=Model%3AMR+2&epid=2065675609&hash=item1e59a9b512:g:M8MAAMXQ1PNRZbGg

Thats not type approved Caroline and should only be fitted to cars pre Feb 2001 mines later 2001 and comes in at from 180 plus post but includes the bolts and gaskets crush rings for the manifold end and wire cone to the exhaust. I checked with Cats4U earlier.

Norman

If it passes MOT Norman which they do why worry?

[Ardent]

The £60 saving has just covered the sensor. Win win.

[BahnStormer]

How about go to a friendly MOT station and ask if they can perform a cat emission test on it. The readings will help you make a more informed choice.
If the CO is high and the lambda reading is correct or close enough you know its the cat at fault..

You still get high CO (and high HC) if the sensor has failed as the engine runs rich, coats the cat in fuel residue and the cat stops working too... so once you've fixed the O2 sensors, one bottle of cataclean and a good (revvy) run and it might be fine...

https://www.mr2roc.org/forum/index.php?topic=64800.msg760204#msg760204

[mr2garageswindon]

The pre cat lambda sensors look after the fueling the post cat sensor is to monitor how the cat is doing, it is often known at the diagnostic sensor as it checks the cat is doing what it is supposed to.
If the sensor is faulty but the other lambdas and cat are fine the CO should be low enough to pass the MOT.
This would indicate the post cat sensor is faulty.
The MRs didn't have a post cat sensor on them.
I would personally get it checked on an emissions tester (Easy for me as I am an MOT station).
Most likely is a knackered cat but I have also seen just the sensor post cat to fail too.

[normanh]

The cars booked in for next Monday for an emissions test, meanwhile, I ordered a Bluetooth reader, what APP can be recommended?
Driven some 80 miles now and no repeat code.

Norman

[1979scotte]

Torque pro for android is good for very little outlay.

Whats the one that @shnazzle likes thats a bit more costly?

[Ardent]

+1 on the torque Pro

Think the shnazzle one is something like dash command. (Could be wide of the mark though.)

[Ardent]

The cars booked in for next Monday for an emissions test, meanwhile, I ordered a Bluetooth reader, what APP can be recommended?
Driven some 80 miles now and no repeat code.

Norman

Happens. 2 trip logic. Could be 10 miles Could be hundreds. (ask me how I know)

[shnazzle]

Torque pro for android is good for very little outlay.

Whats the one that @shnazzle likes thats a bit more costly?

You mean ELMScan Toyota?

I only use Torque Pro and ELMScan Toyota. 
The latter really only for deeper diagnostics of VVTi and stuff that torque can't read.

[Petrus]

Left field solution: If it´s just the sensor, then a distance piece is cheapest.