W164 ML280 MAF or ??

[Crawford]

Folks,

Would really appreciate some advice on what to do about the following set of codes, on a 2008 ML280. The symptoms are an EML, no kickdown and very poor performance.


P0100 MAF/VAF sensor Circuit malfunction

P0101 MAF/VAF sensor Range/performance problem

P0102 MAF/VAF sensor Low input

P0245 Turbocharger (TC) wastegate regulating value A Circuit low

P0489 EGR system Circuit low


P1100 MAF Senor Intermittent/ Check of all OBDII systems not complete

P1102 MAF Sensor In range but lower than expected


P2009 Intake manifold air control actuator, bank 1 Circuit low



I took the MAF references at “face value” so fitted a new:

• Air duct with mass sensors
• Oil Separator breather valve
• Removed/Cleaned/Refitted the EGR valve.

And it hasn’t made any difference – all the symptoms remain…….

I am now wondering if the P2009 sits at the heart of the problem, but would really appreciate some advice!

 

[Crawford]

And so, dear readers, an update: after searching the forum for similar cases, i came across the suggestion to check the fuses. Ooops.

I did, and number 104 in the engine bay (15A) was out. I replaced it, road-tested and found the car was better for a while - but then returned to the low performance pattern described above. On re-checking, fuse 104 has blown again.

This has me thinking about turbo actuators - could these then mean that the MAF sensors are reading low too? Or just lots of problems?!

On looking at the actuator, the lever at the back seems "wobbly" - not like one would imagine it is meant to be.....

 

[Jobsworth]

Commonly the egr valve or the swirl flap actuator motor can both blow the fuse. Disconnect them one at a time and try again with a new fuse to see which is responsible. It’ll run in limp with either disconnected, but you are only trying to identify which component is blowing the fuse

 

[DSM10000]

I am afraid you are suffering from playing parts darts.

A scan with Star (by someone who knows how to use it) would have saved time and money. As you have found certain codes are triggered by other faulty components /and or power supplies.

 

[Crawford]

Will give Jobsworth's disconnection-based fuse test a go ASAP.

I would have tried an indy, but the last MB specialist i went to - who was, i think, recommended on this forum or another MB one - was absolutely awful. The most condescending and un-mechanical garage i've been to in a lifetime of car stuff. Put me off trying another.

So, now it is me - whoever is reading - and a bag of fuses.....

 

[DSM10000]

Will give Jobsworth's disconnection-based fuse test a go ASAP.

I would have tried an indy, but the last MB specialist i went to - who was, i think, recommended on this forum or another MB one - was absolutely awful. The most condescending and un-mechanical garage i've been to in a lifetime of car stuff. Put me off trying another.

So, now it is me - whoever is reading - and a bag of fuses.....

One bad experience and you are letting it permanently affect your choice of potential help?

I am sure if you let us know where you are based then other MB specialists could be recommend

 

[Crawford]

[TLDR: A digression]

I don't suppose it will be permanent: i will be stuck soon enough, and need an expert's help!

In fairness to the garage, it was my interaction with just one of their mechanics not the people who ran the place.

Really assertive and "alpha". He announced that neither my 08 ML or my father's 07 S65 could be expected to work - "they are old cars now" - and probably wouldn't be worth spending money on if they need repairs. I could understand if he was ultra-committed to the newest stuff only, even if these are hardly the views one would expect at an Indy specialist. However, he then proceeded to tell me that what we really needed was something like his 01 CL500.

Odd. He even proceeded to tell me i should make sure i always use the footbrake - "because it wouldn't be safe on a farm if i didn't".

Left feeling dismissed, belittled and generally told-off! Which wasn't what i was there for!

 

[DSM10000]

[TLDR: A digression]

I don't suppose it will be permanent: i will be stuck soon enough, and need an expert's help!

In fairness to the garage, it was my interaction with just one of their mechanics not the people who ran the place.

Really assertive and "alpha". He announced that neither my 08 ML or my father's 07 S65 could be expected to work - "they are old cars now" - and probably wouldn't be worth spending money on if they need repairs. I could understand if he was ultra-committed to the newest stuff only, even if these are hardly the views one would expect at an Indy specialist. However, he then proceeded to tell me that what we really needed was something like his 01 CL500.

Odd. He even proceeded to tell me i should make sure i always use the footbrake - "because it wouldn't be safe on a farm if i didn't".

Left feeling dismissed, belittled and generally told-off! Which wasn't what i was there for!

I can well understand your reluctance to got back but perhaps a word with the owner might have been in order.

I can imagine this character losing business for his employer.

 

[Crawford]

You're probably right, but i didn't feel like getting someone in trouble: i'm sure he has bills to pay too.

And I wasn't sure if it was me who was "out of touch" - perhaps my cars really are that rubbish. And garages have to be places with foyers full of leather sofas.

If they are, they aren't the ones for me!

 

[Crawford]

And on the matter of the car which isn't at a garage.....

Fuses arrived this evening, so fitted one, disconnected the EGR wire and went for a drive. At least, i think i disconnected the EGR: is it the larger of the two electrical connections to the EGR? There is a smaller one under the heat shield which i left connected. [Q1] Did that need to come off too?

Driving a few miles, the car seemed much better - but certainly not in limp mode: it was revving better than it has in ages.

I was about to do stage 2 of the process, but then discovered that the electrical connection to the swirl flap motor is underneath the large air duct. At least, that is where it looked like on Youtube - [Q2] is that it? Is there one on both sides?

I didn't have time to do it this evening, which gives me a chance to check if that is the right thing before i take things apart......

If it is down there, [Q3] is there any reason not to get a resistor in-hand before i take things apart? That way, whether or not the swirl flap motor is currently the thing blowing fuse 104, it won't have a chance to cause mischief in the future......

Above all, really appreciating the help on here! And the chance to grumble!

 

[Jobsworth]

If the fuse hasn’t blown with the EGR disconnected you might have already found your smoking gun. I’d be inclined to test it a bit longer to be sure, then reconnect it and see if it blows in short order. This is a field-test method of narrowing down the fault, but if you are methodical it can be pretty accurate

 

[Jobsworth]

A resistor in hand is always a good idea for diagnostic testing. If you were in West Sussex I’m near enough for you to grab one. I have hundreds of them

 

[Crawford]

Right then, will try and get a few miles under the wheels in the next day or two and see what happens.

For context, can i leave the EGR disconnected in the long-term? Would have wondered about coding it out - naughty i know - but i get the impression that this is difficult to do on these? Something about a frequency modulated signal not a simple voltage?!

 

[Crawford]

PS - Q1 = Yes, it is the big electrical connector on the EGR.

Q2 = The swirl flap connector is under the MAF?

 

[Jobsworth]

Right then, will try and get a few miles under the wheels in the next day or two and see what happens.

For context, can i leave the EGR disconnected in the long-term? Would have wondered about coding it out - naughty i know - but i get the impression that this is difficult to do on these? Something about a frequency modulated signal not a simple voltage?!

You’ll incur the wrath of some on here if you talk about coding it out. I did resort to this myself towards the end of last year when EGR valves were on back order with Mercedes. After they pushed the date back a third time the customer wanted the car back, so I coded it out. My guy can only do them with the ecu on the bench. It’s all back together properly now before anyone jumps up and down.

 

[Jobsworth]

PS - Q1 = Yes, it is the big electrical connector on the EGR.

Q2 = The swirl flap connector is under the MAF?

Yes, situated between the fuel filter and the turbo

 

[Crawford]

Great, thanks!

 

[Crawford]

Stage 1 road test complete - the best 25 miles the car has done in ages.

How many more miles should i do before i can conclude that the EGR is the culprit? Keen to plan my weekend work, and whether i should be doing the swirl actuator test or ordering another EGR......

 

[Jobsworth]

Maybe put the plug back on and see if the fuse blows soon after. If it does you know what’s doing it

 

[DSM10000]

Stage 1 road test complete - the best 25 miles the car has done in ages.

How many more miles should i do before i can conclude that the EGR is the culprit? Keen to plan my weekend work, and whether i should be doing the swirl actuator test or ordering another EGR......

Did the CEL illuminate during the drive ?