I’m looking for technical help or recommendations on: Faulty catalytic converter
Hi folks,
Since buying my 5 last summer, I have been troubled with a persistent engine management light that only seems to trigger on longer journeys of an hour upwards at motorway speeds. My code reader showed a P0420 code for inefficient catalytic converter which made sense as the previous owner had driven the car with a misfire for a week and therefore I assume, damaged the cat (a little fact he didn’t disclose until after my purchase).
However, since being fitted, the EML has triggered again. The same P0420 code and in the same conditions (hour plus motorway journey). I have checked the O2 sensor readings and they appear to be working (ie not reading 0v). Have I just bought a dud cat? Or could there be another possible solution?
MX5City are a competitor but we also work together, referring business where possible which you will appreciate is as good as it gets with mutual respect.
I do not know who manufactured that cat is but would expect it to be one of the preferred aftermarket manufacturers; please get back with that info. Price seems very fair, somewhat cheaper than me as it goes.
I would suggest that the P0420 code is a catch all and a number of potential reasons…
Damaged catalytic converter (most common)
Oil contamination in the catalytic converter
Incorrect placement of the catalytic converter
Damaged upstream or downstream oxygen sensor / faulty wirings
As this has occurred on a new cat as well as your old part, I suggest that the fault lies elsewhere.
If the misfire had put enough neat fuel into the exhaust system to superheat and melt the front of the internal core, the damage should be obvious. If the part was aftermarket just cut the front pipe section off to inspect. If original cut front pipe section off to check and then SELL IT:-)
It does seem that the previous owner has not been honest with you, so I would take his/her input with a pinch of salt. Justify the cat replacement by inspecting the old cat where possible and then look elsewhere. I am sure that MX5City cats will have a guarantee but I very much doubt there will be grounds for a justifiable claim on that.
an Emissions report photo or at least some details off that would be useful. HCC ppm is a good place to start.
How do you check an EGR valve? They always look very dirty at the business end.
If they let go at the stepper motor, often take out the ECU.
Stepper gone and parts on ecu both create a P1499.
I’ve booked the car in to be checked for an exhaust leak and for an emissions test to see if the cat would even pass the MOT. I shall ask about EGR valve whilst its in.