[Closed] Gnusmobile fault code help please

Will you get home?  Probably.  On my car the fault codes have a mileage stamp on them and a number to show how many times its occurred.  So if it only happens once and then hasn't happened for a while, you can ignore it.

Could be lots of reasons for it though.

https://parts.olathetoyota.com/p0420-code-toyota

Several things can cause a P0420 code in a Toyota:

Leaded fuel in an unleaded system will nearly always trigger this, given the differing properties of leaded fuel combustion and exhaust.
Failed O2 sensors or connections are also possible culprits.
A failed catalytic converter.
Other less likely problems: an issue with the coolant temperature sensor, an exhaust manifold leak, a spark timing issue, leaking fuel injectors, misfires, or fuel oil contamination.
Because there are a lot of possible problems that could cause a PO420 code, it's a good idea to check the (far cheaper) oxygen sensors and other items before you invest in a new catalytic converter.

It seems you will get home, however, the car might need some work to pass it's next emissions test at MOT.

A swift Google of the code has pointed to the O2 sensor(s) being the most likely culprit, followed by a some other bits up to and including the catalytic converter being worn out if you're unlucky.

It should be fine to get you home, but I'd be looking to at least change the sensor, as they're not too expensive by the looks of things, and if it's feeding bad information back to the cars brain then it may wear out the cat with time, which will be expensive.

I have that intermittently on my 07 car...basically means the catalytic converter is on its way out, it is old after all. I did change the pre & post cat o2 sensers but it does still come back periodically; sometimes after a long motorway run.

If you just need to keep the car going, I'd not worry and clear the fault then monitor. I have a cheap Bluetooth odb2 scanner and i use that when it pops up.

Id take it back to the garage you got it from.

Probably a right bunch of cowboys.

That code shows a problem with the exhaust emission, but it shouldn't significantly affect the running of the engine. It might be slightly down on power if the engine computer is trying to compensate but should get you home, and shouldn't be a reason to worry about using it in the short term.

https://www.p0420.com/ is a good site to look at

Some faults with the cat can be helped by an "Italian tune up" - that is, getting the exhaust really hot to burn off any contamination. I'm guessing that the Gnusmobile was working fairly hard on the journey anyway, so that's probably not useful in your case. I have seen it happen when driving slowly in traffic, and it did burn off in that case.

An easy diagnostic thing to look for is whether there are any leaks from the exhaust. If air is getting in, it can confuse the sensors so that the computer changes the fuel/air mixture, which then affects the cat.

Had a 2000 MR2 and it was common for the oxygen sensors to fail. Think the Yaris had the same issue so would check that first as it should be a cheap fix.

You could also try a cat cleaning additive...

Sudocream?

It'll be one of the sensors or a failing cat. Tbh it doesn't matter. Ignore it till the next mot

Dude, you broke it already!

Bad Gnusmas.  I want you to sit in a corner and think about what you've done.

Sorry Mr Cougar ☹️

Nice to see it get used 🙂 Always love a PEaks trip.

When it departed here there was a little hole in the exhaust pipe just in front of the cat, which Marko wleded (I think pics in the Voyage thread) Is it possible it's realted to that? I don't ever recall seeing a sensor anywhere near the cat itself but maybe it's causing something to back up towards the engine? I am not a mechanic.

If it is that then it's not horrendously expensive to fix, exhaust section including the cat is about £80, link to a suitable part in the original thread. It's a bolted join in front of the cat but a welded join behind, it was my lack of welding skills which lead to it departing here with the hole still in place.

Relax and ignore it.

Both my 03 Avensis and my partners 04 Corolla have the engine management light permanently on due to this fault code. Makes no difference at all to driving it. I clear the codes so the light goes out for the MOT each year and both of them sail through the emissions test. The lights then come back on within a couple of days. The dude at the garage says it's always just a dodgy sensor and pretty standard on older Toyotas.

I think half the cars in British Columbia have bad O2 sensors!

My dad's Yaris had that code for 4 years and it was due to the O2 sensors playing up.  They never failed, just would give a bad reading once every few months then resume behaving normally.  Strangely it stopped doing it for a while after we fitted a new battery but then resumed the next winter!  Never got them fixed and the new owner is still driving it 2 years later.

Thanks all. We are now over half way home, just stopped for a leg stretch and toilet break and still going strong. I can honestly say the little tardis, sorry yaris has grown on me a lot.

Good little car 😊

O2 faults are really common. I'd clear it give it s thrashing n then ignore it

It's worked for 8yrs on my mum's corsa.

If they do short trips the don't get hot enough to burn the shite of the sensor....

My 2001 Yaris has had an engine light / sensor failure for about 8-9 years - it continues to pass its MOT every year without fail. Seems it's a common problem with Toyotas.

Thanks for posts i have the same car so probably would have panicked if the fault code came up.  I once asked for the cam belt to be replaced but there isn't one, it's a chain.

I hope its going to be ok, its really sad on here when someone loses a cat....

Catalytic converters don't seem to fail very often in their own.  Mostly they get clogged by oil/fuel/coolant getting past the seals and gumming them up.  The 02 sensors on either side of the cat. send readings to the ecu which compares the amount of 02.  The first to set the fuel mixture and the second to see how the cat. is working.  A dirty air filter, intake leak, exhaust leak, dirty injector etc. etc.  Can cause this error code.  The post cat. O2 sensor leads a hard life so will get dirty and get slow.  If they are heated O2 sensors the heaters are the main failure point  - without that they read incorrectly until they do get hot through the car running.  If the MIL came on shortly after the car was started, not in the middle of a motorway run that's where I would look first.

If you don't experience a loss of power it is unlikely the cat is actually plugged although it may be dirty.  Keep an high on fuel mileage - if it starts using more fuel it should be looked at because long turn rich mixture can damage the cat. and they are often expensive. Watch for rough running especially when warm, power loss, increased fuel use.  If none of those appear, you've probably got a flakey O2 sensor (old, dirty, etc) or one has lost its heater.  If it has lost it's heater it'll be wrong when cold but probably fine when hot, but it'll still set the code.

If it is common on Toyotas that don't seem to have any other problems, it is almost certainly the heater.

Did you get to the bottom of it in the end?

Thread resurrection 😁

No, I haven't got to the bottom of it yet, been a hectic week. The light has gone off again but will get it looked at in the new year probably.

Also reminds me I haven't dropped the obd tool back to Ambrose, completely forgot about it. Sorry Ambrose 🙁