Going into limp mode

[mikerd4]

My 09 CLS 320 CDI is going into limp mode. I took it to my mechanic to scan the codes (the engine light only came on about 2 mins from my mechanics). He cleared all codes but 2 came back instantly.

I think they were Maf fault, and inlet positioner motor sensor. As he isnt that familiar with Mercedes he has contacted his friend who has the star diagnostics and is going to refer me to him once he has spoken to him.

Any one any idea if this is a common enough fault on the 3 litre v6 diesel, is that one sensor that is causing 2 fault codes to pop up?

 

[AMGeed]

Try unplugging the MAF sensor and see if it still runs in limp mode. If it does, your MAF needs replacing.
But a genuine MAF too and not a cheap eBay one. It won't last.

Star diagnostics and an experienced user should pin down the fault.

 

[mikerd4]

Without sounding silly, which one is the maf sensor?

 

[GordonTarling]

Fairly certain that your engine will have two MAF sensors - they're located on the air inlet ducting close to the airfilters. The STAR will diagnose the fault more precisely.

 

[grumpyoldgit]

Without sounding silly, which one is the maf sensor?

The MAF sensor fits sideways into the large diameter (2" - 2½") plastic / rubber hose which runs from the air filter box. 2 x screws hold it in place.

Here's a picture of it mounted (right hand side) in the aforementioned hose. You obviously don't need the plastic hose section if you need a new MAF.

Link to picture FOR MERCEDES S-CLASS W220 S320 3.2 CDI DIESEL (2002-2005) MASS AIR FLOW METER | eBay

Mine failed a couple of weeks ago and threw up the EML. Local MB indie tried a BMW he had handy to check if the fault code would recur after clearing it and before ordering a new MB one. Cost about £50.

Edit: May be incorrect info. The above is possibly correct for the inline 6 cylinder and not the V6.

 

[mikerd4]

When I had a bmw my local indy used Mercedes MAF sensors as they were the same sensor as bmw use but cheaper to buy.

Will have a look and see if I can clean it. I know what a maf is just a little unsure where and how to remove it on the 320 engine

 

[AMGeed]

Cleaning them rarely works.

 

[Mercland]

Its not the MAF, its the inlet port... They work off the same circuit.

Inlet Port Shutoff Motor needs to be changed,... and do it now before it damages the Turbo actuator.

Cost should be less than £500 inc labour.

 

[mikerd4]

Ah feck, any idea of a part number? Im guessing when it goes it throws up both codes?

 

[Mercland]

no not always but the inlet port is going to be the issue...
the MAF code will most likely dissapear afterwards.
I think we have only ever replaced the MAF on a V6 engine once.. comes as the pipe with both MAFs on.

 

[mikerd4]

Thanks for your help. Im trying to sort it with indys over here in Ireland at the mo

 

[mikerd4]

Its not the MAF, its the inlet port... They work off the same circuit.

Inlet Port Shutoff Motor needs to be changed,... and do it now before it damages the Turbo actuator.

Cost should be less than £500 inc labour.

Big thanks for this advice, 100% correct. Got it replaced with the leaky seals on the turbo. Cost me €480 so not too bad either