Teutonius

Hi! I have a W212.002 from 2011, E220 CDI BlueEfficiency (OM651.924). Recently I had a coolant leak and the shop swapped the filter housing bracket and the leak was solved. A month before that, the car also underwent a repair due to an oil leak, where the mecanic went in deep and changed several coolers and gaskets.

However while the coolant leak was developing, I got several strange errors, such as the Comand sometimes going into anti-theft protection, the red «Without changing gear visit workshop» and the cooling fan going on and off while the engine is off, draining the battery.

The Comand message hasn’t been seen for a while, the red Workshop message does pop up now and then but the car works fine as well as the gears (automatic), but the fan still behaves eratically. Also sometimes it doesn’t run even though the coolant temperature is 90-95 C.

I took off the fan connector and applied contact spray, as well as on the connectors on the ECU, no change. Also checked all fuses on the driver’s side under the bonnet, they all seem ok.

When running a fan test in Xentry, I can run it all the way from 10-90% and that works fine.

attachments:
- vertically filmed erratic fan behaviour with engine off and key removed: Erratic behaviour of cooling fan while engine off Mercedes W212 E220 CDI 2011
https://youtube.com/shorts/d1u1C-5VA2E
- pictures of Xentry showing fan error codes and gear error codes

Gear error pt 1

Gear error pt 2

Gear error pt 3

Fan pt 1

Fan pt 2

CaliBenzDriver

You've done a great deal of excellent research
so now, we don't need to start with the basics you've covered...


What do all your Xentry troubleshooting steps tell you ?
Can you summarize fan control vs . other modules ?
how can we help??

Teutonius

To stay with the fan control, it asks whether it is in limp mode, but how can I tell? I am wondering where the cause of my error lies, considering that I can actually actuate the fan fine with Xentry but it isn’t behaving as it should in normal use and while the engine is off. Perhaps this is a known error, what else could I consider doing in order to get closer to the cause of this issue?

CaliBenzDriver

don't beat yourself up...its a sticky topic.

The fan has many ways to act up. Few ppl have seen it all to hand you an easy fan fix.

Fan needs to receive a signal for it to stop. It's fail-safe design.

Fan spinning freely instead of sleeping suggest the PWM signal connection from ECU to fan is calling for attention. Scope is best or a frequency counter to see 10% duty cycle.

ECU may be questionable if signal missing.


Fan restarting after a normal sleep places the issue somewhere else.... Front-SAM sending power to fan while ECU has no power to generate "10% duty-cycle: fan-Off".

At that point you can question CAN Network chaos... start with Reboot then scan whole chassis to see what's happening.
🤞

S-Prihadi

In an OM651 diesel engine as of Jan 2010..... here are the fan wires connection :

Pin 1 is a 10mm brown wire to W9 ground stud, so negative main power - same as most engines, gasoline too.
Pin 2 is a 10mm red from F32 prefuse block, source is MR4 connection from fuse 154 or 151 of 100 amps. This is Circuit 30, so always HOT, main Positive Power. Same with most other engines.

Pin 3 is from Front SAM. THIS ONE IS A LONG READ.

Pin 4 is 0.75mm green-blue wire , it is a LUES signal from N3/9 ( Diesel ECM ). Gasoline ECM is called N3/10
LUES signal is PWM, the speed control signal.


Supposedly if PWM signal is lost, fan will go for top speed.
I never actually tried this test ....yet
Test with Xentry 10% as OFF and above that as ON and maximum speed is at 90% PWM is true. That I have tested, but Ignition has to be ON, that means Pin #3 get +12V from Circuit 87M already.
With engine OFF ignition key out, Circuit 87M will be lost/gone.

I recalled removing a w204 C200 of 2010, its ECM M271.8 without disconnecting the battery, the fan never kicks ON.
By right disconnecting both ECM connectors, the PWM signal is lost for the fan ( pin #4 of the fan ).


But faulty ECM has made fan goes top speed while engine is OFF.
Funny enough some guys found out that low battery can also cause fan to run on its own with engine off.
Search in you tube " w212 fan running with engine off"


Pin #4 signal from ECM. The PWM




Pin #3 ---------------------> 2 images



.
Pin #3 ------




.
Source of power of Pin #3, from Front SAM if for your diesel engine, I am VERY confused because the wiring diagram drawn with error , it goes to NO WHERE !!
This is the wiring diagram I am using , because this is for engine after year 2010.Mercedes-Benz AG, 9/25/24, L/10/20, pe07.16-p-2101-97dal, Wiring diagram for common rail diesel injection (CDI) control unit

Page 1 of 2

Engine 651 as of 6/1/10 in model 212 (except 212.098/298) except code 494 (US version) except code U42 (BlueTEC diesel exhaust treatment (SCR)) except code U77 (Diesel Emission control BLUETEC (SCR)) Control unit N3/9, vehicle connector





.
Look carefully, the pin #3 from the fan is NOT into connector 3M pin 4, it goes to no where !!! Connector 3M Pin #4 goes to Starter, that is Circuit 50.



.

One more time, this time I marked the fan pin #3 wire as green and the connector 3M pin #4 I use Xentry coloring






On my engine, M276.8 3.0 Turbo and also most gasoline engine, the fan motor pin #3 will go to Fuse 22. Connector 14M pin #7 of Front SAM




View from ECM wiring.




But........but, if I use the OM651 wiring of UP TO 5/31/2010 or 31st May of 2010...... the fan pin #3 is the same source as most engine, it is the Front SAM fuse 22 or connector 14M pin 7


.






I once seen OM651 wiring which does not make sense. I think it was around the heater region.
But since I never touch OM651 in my life, I do not know if the actual wiring is that way.




Pin 1 and 2 is self explanatory




Now, you can do these test.


01A. Measure with duty cycle meter capable DMM, when that fan is doing its nonsense spin while engine is OFF. What duty % are you getting ?
Measure pin #4 and any good metal ground of car.

02. Use a second DMM, voltage function only. At the same time with test 01A or 01B.
Measure the voltage of pin #3 and any good metal ground of the car.

01B. Engine OFF and fan not yet doing its nonsense. Set up both the DMM as per test 1A and 02. Knock on the ECM a few times, see it that can trigger the fan doing its nonsense.


Good luck with the test...