Engine misfire caused through faulty nox sensor

[nathane123]

Hi everyone,

I'm new to the forum and would like some advice from anyone who can help.

I own a 2008 BMW 3 series e90 m sport and recently had a diagnostic done after noticing a slight misfire and the check engine light coming on. The diagnostic found five faults in the ECM and they are as follows:

2AF4 Nitrogen Oxide Sensor, electronic / 2AF2 Nitrogen Oxide Sensor, lambda linear / 2AF6 Nitrogen Oxide Sensor, lambda binary / 2EF7 Map Thermostat, activation / 29CF Combustion misfires, cylinder 3

I've been looking online for information about nox and lambda sensors but while i feel i have a small understanding of them i'm not sure i understand them entirely.

If anyone is able to shine some light onto the issue that would be really helpful. I know I could take it in to a mechanics but if i'm able to do it myself then i'd prefer to do that as I quite like working on my car and who doesn't like saving a little money by doing the job themselves.

Thanks in advance.

Nathan.

[Elliot2000]

The nox sensor is not going to be a cause of your misfire - it will almost certainly be the injector on the cylinder logging the misfire- it may also be a spark plug or coil.

It’s all diy-able. I suggest start by replacing coil and spark plug on that cylinder as it’s cheap and easy and if the fault remains it’s time to look at changing the injector - it’s not too bad to do but make sure u replace the injector clamp the correct way as I have seen a fair few where people have stuck them in upside down.

I would also personally ignore the nox sensor Faults

Edited by Elliot2000 on Friday 11th September 19:03