Mercedes C Class EML !! Advice needed!

[6C4GTS]

Morning all
I've been struggling with my C Class 2003 180K daily driver recently.
The EML came on and my indie (usually good) looked at it and replaced some engine air hoses - EML went out for a few miles then back on.
So the car went back and the manifold etc was stripped to replace the air hoses at the bottom of the engine - EML went out for a few miles then back on.
The post cat lambda sensor has now been replaced - EML went out for a few miles then back on.

Next step would appear to be the other lambda sensor and then the cat!!

Diagnostic is saying Sensor 1 Bank 1 but not much more interms of clues.

I am beginning to think we are just replacing things for a laugh.......at my expense.

Anyone got any better diagnostic ideas or advice.

TIA

[Pumaracing]

Sensor 1 is the pre-cat sensor and that's basically all the info we or anyone else have at this stage. Might be worth taking it to an MOT centre and giving them £20 to check the emissions. If those are a pass then you might as well live with the light on as pay a fortune replacing bits at random that aren't actually causing a real problem.

I'm not sure why anyone would replace air hoses if the diagnostic is sensor 1 but maybe there's more to the story than you know.

[6C4GTS]

Thanks - hopefully I picked it up wrong and it was teh pre cat lambda that was replaced.

The car failed emissions on CO and lambda - which is what lead to the sensor change. Car passed emissions after sensor change so I was happy that it was fixed.........until the EML came on again.

Could it be that both sensors are/were faulty and that the diagnostic just picked up the first fault?


Am I in danger of replacing good lambda sensors when I actually have a failed cat?

[6C4GTS]

Yep - confusion over which fault and which sensor was replaced.
Fault was Bank 1 Sensor 2 - so post cat sensor was replaced.
Pre new sensor there were 4 faults adn high emissions - now its still showing 1 indicating a low voltage??

[toger13]

if the partial load breather hose has split which it sounds like it has after it has been replaced the ecu adaptation values need resetting

it faults the o2 sensor because the engine is getting more air than the air mass is seeing

Si