P0430 Catalyst System Efficiency Below Threshold Bank 2

coneybiller · March 17, 2014

Have the EML on on my GS450h, read the fault codes and I have 2 fault
codes that are identical (P0430). I cleared the fault codes and it stays
off for a day, then as soon as I go above 60mph the next day, it comes
back on again, the faults are stored and not current codes. I've not
noticed any MPG loss or loss of power whatsoever! So am I safe to
assume its not the catalysts? Only other thing I could think of is an o2
sensor gone bad perhaps? I don't want to spend money really as I'm
about to sell the car for a more economical one for my 150miles per day
commute to work! Just had all 4 wheels refurbished too which set me back
a fair amount, now this! AAAAARRRGGGG!

Any ideas or experiences/fix stories of this fault?

ColinBarber · March 18, 2014

It is probably one of four things. A faulty/slow sensor after the Cat, the cat itself, a leak in the exhaust, or a faulty/slow sensor before the cat (upstream) which is being detected by the the downstream sensor. In theory the later shouldn't occur, you should get an error code related to the sensor which is actually faulty however this isn't always the case.

I would think it is unlikely to be the cat however they don't normally suddenly fail, their efficiency reduces slowly over time so you may not notice a sudden drop in performance or economy.

Without further diagnosis by monitoring the sensors whilst the engine is running it is difficult to advise where the fault is. Personally I would guess that it is one of the upstream sensors - these tend to fail first as they are subjected to the most amount of heat.

coneybiller · March 20, 2014

Sorry for late reply, this is the first time I've checked back since my post! Thanks for the responce, the cars now on 161k so its had a fair few miles of heat, carbon and fumes being filtered through them! I'm really hoping that the cats havent given up as thats going to cost well over £1k :(

Its also as you say not the easiest diagnosis seeing as it will need to be driven while monitoring upstream and downstream sensor readings! I managed to do 165miles the other day without it coming on! Then not long after i exited the motorway in reading it decided to come on! Typical! I wonder if a bottle of cataclean would perhaps help the isse? I'm slightly worried now I think about it, that I used ZX1 extralube in with my oil and wondered if perhaps this additive could of had an adverse affect on the cats. It does say catalyst safe on the instructions but it seems a coincidence that it came on not much longer after I used it (within a week)!

ColinBarber · March 21, 2014

a quick emissions check will tell you if the cat is working. I suspect that if the ZX1 was responsible it would have affected the air/fuel ratio upstream sensor rather than the cat.