I'd really appreciate a hand diagnosing a slow drain on my battery. I have connected am ammeter in series with the battery negative, defeated the doors and waited 30 mins for the car to sleep.

- I have a steady drain of 117mA (which I averaged over 15 mins anyway, min 114, max 182mA)
- when I remove fuse 101 this reduces to 37mA (again steady)

Car is VIN WDC2510212A129114 with engine 642872 so googling around I this fuse 101 is "O2 sensor upstream of CAT"

- has anyone else heard of an O2 sensor causing issues, with the ignition off, key out, car asleep?
- does anyone have a wiring diagram for fuse 101? NB this varies by year / engine I think. This is a 2011 W251 R class, 6 cyl 3L diesel engine 642872.

As an addition, my electric cooling fan started up (full blast) when I put fuse 101 back. Still ignition off, car asleep. I have had issues in the past with the fan coming on full after a journey, which I resolve by turning the ignition back on and off. This is separate to the slow drain above. But a known 'funny' with this car. Could the two things be related? Is the fan on fuse 101 also? Could it be a dodgy fan controller in fact not the sensor???

Many thanks!

 

OK I carried on looking at this... with the fuse 101 removed I get these fault codes:

1 297 00 - The diesel particulate filter is defective
1 00D 00 - The lower limit value of component B2/7 (right hot film mass air flow sensor) has been reached
1 00E 00 - The lower limit value of component B2/6 (left hot film mass air flow sensor) has been reached
1 01 5 00 - The lower limit value of component B2/7 (right hot film mass air flow sensor) has been reached
1 01 6 00 - The lower limit value of component B2/6 (left hot film mass air flow sensor) has been reached
1 20D 00 - Component Y77/1 (charge pressure positioner) has short circuit to ground
1 21 5 00 - Component M55 (intake port shutoff actuator motor) has short circuit to ground
1 61 4 00 - Component B2/6b1 (left intake air temperature sensor) not within permissable range of values on/off ratio is reference signal is outside of permissable range
1 61 5 00 - Component B2/6b1 (left intake air temperature sensor) not within permissable range of values there is a frequency or pulse width modulation fault
1 61 7 00 - Component B2/7b1 (right intake air temperature sensor) not within permissable range of values on/off ratio is reference signal is outside of permissable range
1 61 8 00 - Component B2/7b1 (right intake air temperature sensor) not within permissable range of values there is a frequency or pulse width modulation fault

And summing that up I seems to have three components to consider:

1. The y shaped intake (which I think houses all of the the left and right sensors)
https://www.ebay.co.uk/itm/174487221148

2. The charge pressure positioner (aka turbo actuator???)
https://www.ebay.co.uk/itm/185760234228

3. Intake port shutoff actuator motor
https://www.ebay.co.uk/itm/174838057725

I think the particulate filter error is probably deduced from pressures not making sense so am tempted to ignore that right?

 

If anyone has any words of wisdom to share on the above / how to continue I'd appreciate it. At the moment....

- I'm not sure it will be a sensor... why would these draw a current in sleep mode?
- Am thinking perhaps it's one of the motors? perhaps a bit fouled up and trying to return to a default position a bit like a seized up windscreen wiper?

So my plan anyway is to pull a few plugs and see if I can make the excess current draw go away.

But if anyone has different ideas / other things I should have a look at then I'd be extremely grateful for advice on this I'm just a DIYer so really not sure I know what I am doing here... thanks.

 

If you haven't seen the DiagnoseDan episode on youtube with the X164 it might be worth a look regarding parasitic drains.

You might be overthinking this. You've got fuse 101 and three potential areas of the draw. Disconnect one by one and see?

Check the video. Its posted here before and also on X164 and W164 forums. If only to make sure your process is good.

 

The answer is yes....drove me nuts....until the emissions recall replaced practically everything under my 2012 ML350 W166 Bluetec, that also affecting my front SAM, passenger side,out wall....I left it so long as to defeat the sam....my bad!

 

Thanks I'll go ahead and see / post back here.

 

OK I've kept going at this..... to re-cap, I have a mystery excess 80mA parasitic power draw on fuse 101. I don't have a wiring diagram, but when I pull the fuse I get fault codes related to:

1. LEFT and RIGHT air flow and temperature sensors (in the top manifold that connects to the turbo)
2. Charge pressure positioner (on the turbo)
3. Intake port shutoff actuator motor (flap valve)

So with fuse 101 back in, doors defeated and the car in sleep mode i.e. waiting 30 mins I then pulled out the connectors to 1&2 above... no change.
Then I disconnected 3 (intake port shutoff actuator motor) and the electric engine cooing fan started running on full. Given that current draw I cannot see for sure whether that was drawing the 80mA or not. Frustrating.

SO I'd really appreciate any words of wisdom:

A. Why would disconnecting the intake port shutoff actuator motor cause the engine fan to run? When the car is supposed to be asleep.
B. Could it be that the actuator motor is fine and in fact a 'good' signal from the unit is causing the power drain elsewhere (e.g. the cooling fan)?

I have always had 2 issues with tis car... a parasitic power drain when parked AND a strange thing with the cooling fan. Sometimes with the ignition off and the car locked it comes on and NEVER stops until it dreains the battery. Could these two things in fact be related? I'm feeling really stumped at the moment. Thanks all.

 

i found the link


watching now

 

Thanks.... it's a really good video.... I had to go through fuse by fuse in my car which took a long time...! But narrowed it down to a particular circuit. However in my case it's not as simple as a blower unit unfortunately I wish it was. I am deep in the engine. But thanks for posting anyway.

 

OK latest is that

- I am definitely seeing 80mA quiescent draw across fuse 101. Measured by taking the fuse out and also the 0.3mV drop across the (15A) fuse.
- Interestingly I am also seeing the same draw across fuse 105. If I unplug fuse 101 then the draw across 105 reduces to zero so they are related.

Both are engine / ECU / CDI type fuses. Can anyone help me wtih a wiring diagram? I tried alldata but they don't cover this car...

VIN WDC2510212A129114 with engine 642872

Many thanks!

 

Anyone?

 

You need to give some more information. Its not as simple as searching up Fuse 101.

Which location are these fuses in? Interior compartment, under hood, rear?
Which circuits/modules do they relate to?

There are hundreds of wiring diagrams. I have your VIN in WIS but there are too many documents to search through

 

Thanks the fuses are in the engine compartment, I'll post a pic and more info below.

 

So I circled the fuses in question. I only have google to go on, but the info I can find is a little ambiguous, as the connections vary by year and emgine type. I think I have a 642872 / year 2011.

From: https://fuse-box.info/mercedes-benz/...uses-and-relay

FUSE 101

up to 2008:
AAC with integrated control additional fan motor
Valid for engines 113, 272: Purge control valve
Valid for engine 272:
Radio interference suppression capacitor 1
Radio interference suppression capacitor 2
Cylinder 1-6 ignition coil

Valid for engine 642:
O2 sensor upstream of CAT
CDI control unit
as of 2009:
Engine and air conditioning electric suction fan with integrated control
Valid for engine 272, 273:
Purging switchover
Circuit 87 M1e connector sleeve
Valid with engine 642:
CDI control unit
O2 sensor upstream of CAT
Valid for engine 642.870/872:
O2 sensor upstream of CAT

FUSE 105

up to 2008:
Valid for engine 113:
ME control unit
Radio interference suppression capacitor 1
Radio interference suppression capacitor 2
Cylinder 1-8 ignition coil

Valid for engine 272:
ME control unit
Hot film mass air flow sensor
Hall sensor for left inlet camshaft
Right intake camshaft Hall sensor
Left exhaust camshaft Hall sensor
Right exhaust camshaft Hall sensor
Left intake camshaft solenoid
Right camshaft intake solenoid
Left exhaust camshaft solenoid
Right exhaust camshaft solenoid
Cylinder 1-6 fuel injection valve

Valid for engine 642: CDI control unit
as of 2009:
Valid for engine 272, 273:
ME-SFI [ME] control unit
Circuit 87 M1i connector sleeve
Valid with engine 276: Engine/engine compartment connector
Valid for engine 642.950:
CDI 1.0 PK control unit
Engine compartment/interior compartment connector
Valid for engine 642.870/872:
CDI control unit
Engine compartment/interior compartment connector
Circuit 87 connector sleeve

 

I have also tried unplugging the fuses to see what fault codes come up...

FUSE 101 gives fault codes on:

1. LEFT and RIGHT air flow and temperature sensors (in the top manifold that connects to the turbo)
2. Charge pressure positioner (on the turbo)
3. Intake port shutoff actuator motor (flap valve)

FUSE 105 gives fault codes on:

1. front SAM
2. Overhead control panel
3. COMAND (MOST comm link broken)

 

By the way.... I'm still wondering whether I actually have a fault, or whether 120mA sleeping current draw, whilst high, is in fact in spec for this car? It is relatively old and packed full of electric gadgets. Is there any way of knowing what I would expect it to draw? Many thanks for your advice and help...... Andy

 

Andy,

OK. Here is the wiring diagram for your VIN as well as other supporting documents. There may be more than you need below, but better you can see them than not. If you need anytjing else along the way, let me know. You'll see the "Search Aid" document lists all the diagrams etc that are available. If you need something on that, mark it and take a photo or scan and send the whole page back to me and I'll find it for you.

Regarding the drain query, its usually something like 50-80 mAmps is considered 'normal'. Others may know more, but 120 mAmps sounds higher than it should be to me.

Nick

 

Brilliant Nick thank you....!!!

 

Im not sure Ive given you all that you might need so just let me know..I'll never be a diesel man so my knowledge is limited on those. Next time buy a gas V8!

 

check one more thing, look at all buttons in your front seats , make sure non of them is push in and stock in , best

 

How did you go?