RX400h error codes P0420 & P0430

[acer54]

Check engine light came on last night, pulled the codes this morning and they are P0420 & P0430, I have reset the codes and will now monitor for a recurrence of the codes.

I have looked at what the codes mean and it's pointing to the catalytic converters bank 1 and bank 2, I've also read that in some cases O2 sensors, MAF or an exhaust leak could also be the cause.

Can anybody advise me what is actually going on, I'm dreading having to replace the catalytic converters as they are so expensive, it's in for MOT later this month so if the emissions are high this will also point to inefficient catalytic converters but I'm hoping it's an easier fix.     

[Herbie]

Unless things have changed in this new MOT, hybrids are not checked for emissions. This is because to get correct readings the engine has to be at a certain temperature but with a hybrid the engine may not even be running, let alone at working temperature.

And in more than 40 years of driving I've never had a cat fail, nor do I know anyone who has, so I wouldn't worry about that too much.

Linky to latest MOT Inspection Manual - and no, hybrids still don't have to be tested on emissions.

[Delphius1]

Codes P0420 and P0403 refer to the catalyst efficiency for cylinder bank one and bank two respectively.

Part of the OBD2 standard is that the ECU has to be able to measure the efficiency of the cat and report any deviations, so the car has oxygen sensors before and after the first cat in the exhuast stream. The first O2 sensor measures the result of the combustion process and the ECU alters fuelling to suit. The O2 sensor after the cat checks the efficiency and that's what these codes refer to.

It's unusual for both banks of a "V" configuration engine to report problems with cat efficiency simultaneously. Usually there's an air leak in the exhaust manifold that allows excess oxygen to enter the exhaust on one side and cause the efficiency code on that side to be thrown. It would be unusual and very unlucky for both cats to suddenly become inefficient both at the same time.

If both banks report problems  it's possible something upstream of the combustion process is causing the issue, so it's possible an air leak in the intake could be responsible, that would affect both banks simultaneously. It would really need some diagnosis to find out the cause. 

A decent diagnstic centre should be able to look at the figures coming out of the ECU via the OBD2 connector and narrow down the cause.

I've seen it before on a car that I modified. The ECU couldn't cope with the amount of air entering the engine so the mixture was very lean, resulting in excess oxygen in the exhaust and tripping the cat efficiency code on the ECU.

 

 

[BachelorDays]

First thing to do is to erase these codes and see if they come back again.

As Delphius1 says, very unlikely both bank CATs have suddenly gone.

If the codes come back quickly then it could be a leak - could also be the MAF.  But first things first..

[acer54]

17 hours ago, Delphius1 said:

Codes P0420 and P0403 refer to the catalyst efficiency for cylinder bank one and bank two respectively.

Part of the OBD2 standard is that the ECU has to be able to measure the efficiency of the cat and report any deviations, so the car has oxygen sensors before and after the first cat in the exhaust stream. The first O2 sensor measures the result of the combustion process and the ECU alters fuelling to suit. The O2 sensor after the cat checks the efficiency and that's what these codes refer to.

It's unusual for both banks of a "V" configuration engine to report problems with cat efficiency simultaneously. Usually there's an air leak in the exhaust manifold that allows excess oxygen to enter the exhaust on one side and cause the efficiency code on that side to be thrown. It would be unusual and very unlucky for both cats to suddenly become inefficient both at the same time.

If both banks report problems  it's possible something upstream of the combustion process is causing the issue, so it's possible an air leak in the intake could be responsible, that would affect both banks simultaneously. It would really need some diagnosis to find out the cause. 

A decent diagnstic centre should be able to look at the figures coming out of the ECU via the OBD2 connector and narrow down the cause.

I've seen it before on a car that I modified. The ECU couldn't cope with the amount of air entering the engine so the mixture was very lean, resulting in excess oxygen in the exhaust and tripping the cat efficiency code on the ECU.

Thanks for your very informative answer, I will continue to monitor the situation and update as and when the codes return.

 

 

 

[acer54]

EML light back on, same two codes, P0420 & P0430, time to get it checked - just a little afraid of Lexus prices, not sure of the alternatives, any ideas anyone?

[Herbie]

2 hours ago, acer54 said:

EML light back on, same two codes, P0420 & P0430, time to get it checked - just a little afraid of Lexus prices, not sure of the alternatives, any ideas anyone?

No need to take it to Lexus unless you particularly want to Steve. The codes relate to the internal combustion engine and emissions, so any good garage/mechanic should be able to sort it. Ask family/friends for personal recommendations or maybe you have a similar thing to our 'Safe Trader Scheme' which is run by Lancashire Trading Standards office.

[BachelorDays]

On 10/10/2018 at 7:25 PM, BachelorDays said:

First thing to do is to erase these codes and see if they come back again.

As Delphius1 says, very unlikely both bank CATs have suddenly gone.

If the codes come back quickly then it could be a leak - could also be the MAF.  But first things first..

A week before they came back again.  That's not quick enough as far as I'm concerned.  Roughly how many miles did you drive during this period and what's the mileage on the car?

If the engine runs smoothly, specially at high speeds, it's unlikely to be O2/CATs.  It could even be something as simple as a loose petrol cap (or a dried O ring inside it).  If it's high mileage, maybe the MAF.

Herbs is right - you don't need the dealer for this.  Anyone with good diagnostics skills will be sufficient.  A specialist in Toyota/ Lexus with a decent reputation will be great.

[acer54]

9 hours ago, BachelorDays said:

A week before they came back again.  That's not quick enough as far as I'm concerned.  Roughly how many miles did you drive during this period and what's the mileage on the car?

If the engine runs smoothly, specially at high speeds, it's unlikely to be O2/CATs.  It could even be something as simple as a loose petrol cap (or a dried O ring inside it).  If it's high mileage, maybe the MAF.

Herbs is right - you don't need the dealer for this.  Anyone with good diagnostics skills will be sufficient.  A specialist in Toyota/ Lexus with a decent reputation will be great.

I drove about 50 miles after clearing the codes, mileage is about 125,000.

Engine runs smoothly right through the range as it always has.

Petrol cap seals OK, only thing of note is these codes only started after the last fill up, I use the same BP garage every time and always use Ultimate fuel, maybe this is a red herring but I thought it was worth mentioning.

If it was the MAF wouldn't  throw a different code?

 

[BachelorDays]

MAF is upstream from all other systems in the mixture/combustion/emission systems.  That's why a problem with it can manifest itself in many different ways.  That's one reason MAF is the first thing that comes to mind - although at times maybe it comes to mind too readily!

Your mention of the last fill up is interesting and may not be a red herring.  If the car is running fine I'd park the MAF investigation for now.  On the petrol cap, do you get that 'whoosh' when you remove it for filling?  I'd still clean around the rim and check the O ring.  But be very careful not to drop any dirt inside the tank filler.  

You could also check for codes a day or so after you've cleared them - these codes will first register as Pending and, only if persistently triggered, will then throw the EML.

[acer54]

18 minutes ago, BachelorDays said:

MAF is upstream from all other systems in the mixture/combustion/emission systems.  That's why a problem with it can manifest itself in many different ways.  That's one reason MAF is the first thing that comes to mind - although at times maybe it comes to mind too readily!

Your mention of the last fill up is interesting and may not be a red herring.  If the car is running fine I'd park the MAF investigation for now.  On the petrol cap, do you get that 'whoosh' when you remove it for filling?  I'd still clean around the rim and check the O ring.  But be very careful not to drop any dirt inside the tank filler.  

You could also check for codes a day or so after you've cleared them - these codes will first register as Pending and, only if persistently triggered, will then throw the EML.

I do get the whoosh when removing the cap for filling, I also checked and cleaned it but it looked ok before cleaning.

The codes do register as pending first and throw the EML later.

[BachelorDays]

You could ride out this tank of petrol - maybe even fill up again half way.  Bad petrol is a possibility but extremely remote.

The other option is to get someone to hook it up and examine the live data.

Still can't rule out a vacuum leak.  You could go over the pipes around the engine, check the air filter housing, etc.  But this is the sort of thing that normally only happens if someone's recently done some work under the bonnet and disturbed something.

[scudney]

don't know if this helps had a P420 on my IS200 when I had a stainless steel custom exhaust made and fitted,it turned out to be a very small hole in the exhaust(the size of a pin) where it hadn't been welded properly was causing the eml light to come on

[Stupot]

I had an EML light come on and went into limp mode on my LS400. I had just brimmed the petrol tank on filling and there was a woosh when I next unscrewed the filler cap. Research on here suggested too much vacuum caused by overfilling. I never over filled again and never had the EML light come back on either. 

[acer54]

59 minutes ago, Stupot said:

I had an EML light come on and went into limp mode on my LS400. I had just brimmed the petrol tank on filling and there was a woosh when I next unscrewed the filler cap. Research on here suggested too much vacuum caused by overfilling. I never over filled again and never had the EML light come back on either. 

I do brim it to be fair, yesterday I had the filler cap off to check the integrity of the seal, I'm using it later today, hopefully the EML light stays off!  

[acer54]

19 hours ago, scudney said:

don't know if this helps had a P420 on my IS200 when I had a stainless steel custom exhaust made and fitted,it turned out to be a very small hole in the exhaust(the size of a pin) where it hadn't been welded properly was causing the eml light to come on

It's in for MOT and service next week, will mention the EML codes and have him check for leaks on the induction and exhaust sides and also check the O2 sensors up and downstream of the cats.

[acer54]

UPDATE

Used it for over a week and no EML, plugged in my code reader and it's clean not even any pending codes were there.

Hopefully it's settled down but would have liked to have known what was throwing the codes in the first place? 

[BachelorDays]

Filling up to the brim is a bad idea - it plays with the system that tackles petrol fumes in the tank and returning fuel.  EVAC, Purge Valve etc are the terms usually associated with it.

At present it does look like it's simply a case of over-filling/ bad petrol (very remote)/ petrol cap.  Obviously no need to do anything at present.  Hopefully won't come back.

If it helps, I had a 2000 Mercedes E240 which used to throw CAT codes every few hundred miles - and ALWAYS after coming back from a trip across the Channel.  Did that for a good 3-4 years.  I thought the tank cap was a bit suspect and at the same time knew the MAF was probably on its way out (MAFs on MBs don't last long).  The car was on its way out so never bothered.  However, never had any issues with MOT, emissions, MPG, French speed cameras.. (although the last one is probably not a CATs issue anyway).

 

[acer54]

18 hours ago, BachelorDays said:

Filling up to the brim is a bad idea - it plays with the system that tackles petrol fumes in the tank and returning fuel.  EVAC, Purge Valve etc are the terms usually associated with it.

At present it does look like it's simply a case of over-filling/ bad petrol (very remote)/ petrol cap.  Obviously no need to do anything at present.  Hopefully won't come back

I've always brimmed all of my cars and never had any issues, in future I will not brim them quite so enthusiastically......