W164 ML280 OBDII Codes - Which of these is the main issue?!

[ezzer]

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!

 

[ezzer]

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.....

 

[Wighty]

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.....

If you are handy , take the actuator off , spray clean the inside with electrical cleaner to get the carbon gunk out , then put a tiny amount of high temp grease on the worm gear inside .
Also check that the small wires that leave the outside edge of the pcb board don’t have small cracks in them .

As you say with the 15amp fuse blowing , the actuator, inlet port motor and exhaust back pressure sensor are all linked .

You can try the resistor fix to rule out the inlet port motor . A 4.7k ohm resistor is put into the middle two terminals of the electrical feed to the inlet port motor (cost £1 ).

Remove the exhaust back pressure sensor by the turbo and spray clean the underside hole with carb cleaner …don’t drop the chrome washer below it !

Egr , remove and clean the muck off it .

These are pretty much free jobs to try .

 

[Uncle Benz]

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

 

[ezzer]

I think i recognise Uncle Benz from another corner of the interweb! But haven't managed to implement this welcome advice since reading there!

Will get on ASAP.....

 

[Uncle Benz]

I answered the same post on mbclub. I literally cut n pasted it. I have a different username, long story

 

[ajlsl600]

A system designed to pump hot gas crud and oil vapour thru a variable opening getting bunged up n blowing fuses, wot a surprise, n. Wot a back street garage design.
Little better than l rover fitting compressors to their v8s (costing 5/10 bhp) and running air pipe into exhaust to dilute gas for USA exports. I once spent an hr lookin at that and wonderin on mentality of lr and their designers benz no better. Cud not say that 25vyr ago.

 

[ezzer]

Right, home-work report......

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. Would have been fully stuck, even with enthusiastic searching of the forum!

 

[Uncle Benz]

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

 

[ajlsl600]

Secret of all this is.. Don't rush...

 

[Wighty]

Right, home-work report......

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. Would have been fully stuck, even with enthusiastic searching of the forum!

The big hole is where the EGR is with its electrical connection below it . The small thing by the turbo shield is the exhaust back pressure sensor (clean the hole below this sensor) .
The swirl motor electrical connection is below the black batwing air intake by the fuel filter . Yes there is only one connection for it . I fitted my 4.7k resistor 4 years and 30k miles ago (?) . Might be worth following @Uncle Benz fault diagnosis procedure first though if you really need to know which is at fault .

 

[ezzer]

Thanks for the picture - worth as many words as people say! Having said which, i am not sure i can make out the hole you are talking about - is it "in" the female part of the upper connector?

Will defo follow the one-step-at-a-time approach of Uncle Benz!

 

[Wighty]

Thanks for the picture - worth as many words as people say! Having said which, i am not sure i can make out the hole you are talking about - is it "in" the female part of the upper connector?

Will defo follow the one-step-at-a-time approach of Uncle Benz!

Clean the hole of this exhaust back pressure sensor when you remove it . 24mm deep socket , watch the chrome coloured washer below it . You will see the sensor hole has black gunk inside it .

 

[ezzer]

Ah, that makes sense - thanks for the extra details. Especially the socket size!

In terms of road-tests, i did about an hour today - on country roads so only 25 miles or so in total. The car drove really well, the best it has in ages. Makes me realise that there was probably some sort of developing deterioration before i reached the point of the fuse blowing, but hadn't spotted it as i had no frame of reference - just one ML!

Does this make it any more or less likely to be the EGR?

I know i am meant to be patient, but how many more miles should i do before i can conclude this is the issue? Keen to plan my weekend work, and whether i should be doing the swirl actuator test!

 

[Uncle Benz]

Put the plug back on the EGR and see if the fuse blows again. If it does you know what’s causing it

 

[ezzer]

Right, will do and - for all those reading with interest now or in the future - will post back!

 

[ezzer]

After another 40 miles, the car continued to drive well - but the CEL is now on.

The codes are P2009 (Intake manifold air control actuator) and P0101 (MAF/VAF - range/performance problem). Fuse 104 remains intact, but haven't tried reconnecting the EGR yet - got too dark!

(More specifically, after hearing that the CEL was on and my partner also telling me that the car seemed "slow and draggy" i thought i should try it as it was, without reconnecting the EGR. Doesn't seem slow and draggy to me!)

My thoughts are that i may have the swirl motor problem, in addition to the EGR one, which can be "fixed" with a resistor. More annoyingly, P0101 means that the MAF sensor i just fitted hasn't worked.

Hope there is some other interpretation!!

 

[Uncle Benz]

I would try a resistor mod. The EGR may be ok, it may not be. A 40p resistor next, good long road test, keep us posted. I have literally 100 resistors in my drawer because that’s the cheapest way to buy them. I’ll give you one for free (oo err) if you aren’t far from West Sussex

 

[Uncle Benz]

Out of interest, where did you buy a new MAF? Did it come complete with the batwing?

 

[ezzer]

Right, resistor mod it is.

Got the MAFs with a batwing. Cheap-ish off eBay, but from a seller who claims these are decent OEM quality and has quite a few seemingly real reviews to say they work.