Exhuast Emissons Light on Where to take Car?

benjus

I've just got a P0420 code on my car for the second time... I guess that's similar to what the OP reported. I suspect a faulty rear lambda sensor because the car passed its MOT two weeks ago with no problems and seems fine to drive. With my trusty £15 USB cable I can reset the code, and last time it took several weeks for it to come back.

If it is just the rear lambda sensor I'm not too worried, as AFAIK it's just there to detect that the cat isn't working properly, but if it passed the MOT it can't be too bad. Is that a reasonable conclusion?

colino

P0420 is a perfect example of the skills, knowledge and experience you need in addition to the code reader/scanner. And that's from the cheap Chinese knock-off to the best of diagnostic equipment.
Beware anyone who tells you, just on the basis of P0420, that it is anything specific without further investigation P0420 can be the cat, a sensor or even a pinprick hole in the exhaust.

benjus

colino wrote: »

P0420 is a perfect example of the skills, knowledge and experience you need in addition to the code reader/scanner. And that's from the cheap Chinese knock-off to the best of diagnostic equipment.
Beware anyone who tells you, just on the basis of P0420, that it is anything specific without further investigation P0420 can be the cat, a sensor or even a pinprick hole in the exhaust.

I understand that, but would the MOT emissions test have flagged something up in the case of the cat or a hole in the exhaust?

This car is old, has high mileage and is not in great condition. I don't depend on it for anything, it's just a runabout. I got it to avoid spending money hiring cars, and I'll feel I came out on top if it lasts me a year. So I don't want to spend any more money on it than is absolutely necessary.

Kilty_2

Can they charge for diagnostics when the car is under warranty?

My car's been into Kia already to try and find the source of a rattle - inconclusive, but no charge. Going back in again in a couple of weeks.

cyclonebri1

Kilty wrote: »

Can they charge for diagnostics when the car is under warranty?

My car's been into Kia already to try and find the source of a rattle - inconclusive, but no charge. Going back in again in a couple of weeks.

No they can't, provided they acknowledge there is a warning showing.
And I dare say they can't under any other circumstances as it would be their choice to interogate it.;)