Lambda / Oxygen sensor on C320cdi 2006 - help!

[Steve Pocock]

Hi all,

Took a look underneath today to check out access to the sensor and give it a spray with WD40 before ordering a new sensor - hopefully to clear the fault codes P0030 P0130 & P0135 and the hesitation followed by limp mode that is getting worse.

I found the oxygen sensor with a 22mm nut fitting but also see a second sensor just upstream of that with a small approx. 16mm nut fitting - what's that for? Its the lower sensor in my photo attached.

I've read conflicting advice on forums about oxygen sensors with some saying there are 3 but others saying there is just the one on 320cdi diesels. My plan was to change the 22mm one just before the cat first and see if that solved my issues...…….

 

[Steve Pocock]

And no one replied to me! Feeling like Billy No Mates here.....

Update - I changed the O2 sensor and cured most of the problem but still get the same hesitation followed by limp home occasionally. Now have zero fault codes though. Could this be the second unidentified sensor I mention above?

 

[alexanderfoti]

What is the code definition for those three P codes?

 

[Uncle Benz]

The 22mm one is the lambda sensor. The 16mm one is exhaust gas temperature sensor. All three codes you posted are for the lambda sensor. I’ve not seen a lambda fault cause limp on one of these though. Have you scanned for codes in other modules since replacing the lambda sensor?

 

[Wighty]

My lambda sensor (E class E320cdi) failure gave codes , but never put it in limp mode .

 

[Steve Pocock]

Since changing the O2 lambda sensor it goes into limp much less frequently but has never given any of the fault codes above - or any others - again. My B service is due in 7k miles so I wonder if new air and fuel filters could help? I intend to replace the troublesome intake gaskets then too - although they show no signs of leakage. I have had the swirl flap linkage changed but that made no difference at all.

I could easily be talked into the root cause of this being the auto 7G transmission and a fluid and filter change - no real reason why other than the sensation that the box often feels as if its not reacting quickly enough for the engine or conditions. I put this down to 20 year old tech and chips but cant believe that when new MB would have produced such an easily confused auto. I wonder if the auto box confusion feeds back into the fuelling demands and thus confuses engine management too.

Such a shame as when its on song its a thing of great beauty to drive. The kick in the back ffom the torque is unique to me. Love it but unreliable power drives me crazy.

 

[Wighty]

Since changing the O2 lambda sensor it goes into limp much less frequently but has never given any of the fault codes above - or any others - again. My B service is due in 7k miles so I wonder if new air and fuel filters could help? I intend to replace the troublesome intake gaskets then too - although they show no signs of leakage. I have had the swirl flap linkage changed but that made no difference at all.

I could easily be talked into the root cause of this being the auto 7G transmission and a fluid and filter change - no real reason why other than the sensation that the box often feels as if its not reacting quickly enough for the engine or conditions. I put this down to 20 year old tech and chips but cant believe that when new MB would have produced such an easily confused auto. I wonder if the auto box confusion feeds back into the fuelling demands and thus confuses engine management too.

Such a shame as when its on song its a thing of great beauty to drive. The kick in the back ffom the torque is unique to me. Love it but unreliable power drives me crazy.

The advice with the 7g box is change the atf and filter every 40k miles , maybe £250 at an Indy

 

[Botus]

my fathers....

12 years and 100k, no issues at all in car's life... then 4 separate incidents in the next 6k miles and 4 years

CAT sensor heater failed.... gave no issues drove the same, no lights, only in diagnostic did you know. Replaced cleared diagnostics (£100)
Glow plug light on, car drove the same... replaced the 6 glow plugs and the control unit with Beru (one new glow plug failed inside 2k miles replaced OK since) (£140)
Car a bit gutless no EML, ragged it about, clearly some boost at high revs, EML then illuminates... Found loads of fault codes and fuse popped. Turns out the usual Swirl flap motor is dead. Did the resistor trick and replace the fuse, car drives better than it used to, less than (£1)
Car flat as hell no lights... Exhaust Back Pressure sensor failed... replaced, car good as new (46)

From what I've read in 6 years on this forum all NORMAL issues that will afflict every one built. after 10 years. If you have a later tractor you'll get these extras in the first 5 years

NOx sensors (£900)
DPF sensors (200?)
Software updates (£???)
Ad blue tank failure (£1900)

 

[Steve Pocock]

I gave up with second guessing what put it into limp mode and took it to a different indy MB specialist. They diagnosed busted turbo and fitted a shiny (EXPENSIVE!) new one. Hey presto - no more limping. Car is now back to going like a train, smooth. Pity my first indy 'specialist' didn't find this before doing another £1200 of work unecessarily!

 

[mioba]

Thanks for updating. its been a struggle, but you got there.