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Hello, I live in Turkey and I am new to the this forum. I have a 2010 model m271 engine w212 e250 cgi car. At 220000 km. I have been experiencing fluctuations in the engine coolant indicator for a while. I also have a problem with the radiator fan. It works unbalanced. After driving the car, approximately 1 or 2 hours later, when I come back and open the door or insert the key, the radiator fan is running at full speed. There was a leak in the radiator and I installed a new one. Thermostat changed. The sensor that measures the coolant on the thermostat has changed. But my fan problem and fluctuation in the coolant indicator continue. As seen in the video, there is fluctuation, sometimes it drops to 0.In the video, the car did this while stopped at the light. As soon as you step on the gas, the temperature returns to normal. It gets better after a while. But it never goes above 100. It doesn't matter whether the air conditioner is on or off. Sometimes it does, sometimes it doesn't. The temperature stabilizes at an average of 85-90 degrees and there is no problem. Sometimes this problem occurs when suddenly stopping at a light. I couldn't solve the problem. Is the thermostat working incorrectly? Or is the temperature sensor cable working incorrectly? I would be glad if you can help.
Hello, I live in Turkey and I am new to the this forum. I have a 2010 model m271 engine w212 e250 cgi car. At 220000 km. I have been experiencing fluctuations in the engine coolant indicator for a while. I also have a problem with the radiator fan. It works unbalanced. After driving the car, approximately 1 or 2 hours later, when I come back and open the door or insert the key, the radiator fan is running at full speed. There was a leak in the radiator and I installed a new one. Thermostat changed. The sensor that measures the coolant on the thermostat has changed. But my fan problem and fluctuation in the coolant indicator continue. As seen in the video, there is fluctuation, sometimes it drops to 0.In the video, the car did this while stopped at the light. As soon as you step on the gas, the temperature returns to normal. It gets better after a while. But it never goes above 100. It doesn't matter whether the air conditioner is on or off. Sometimes it does, sometimes it doesn't. The temperature stabilizes at an average of 85-90 degrees and there is no problem. Sometimes this problem occurs when suddenly stopping at a light. I couldn't solve the problem. Is the thermostat working incorrectly? Or is the temperature sensor cable working incorrectly? I would be glad if you can help.
Good deal! Melhaba, we'll help you if you promise Turkiya will keep making the best sun dried apricots in the world
swinging temps + CEL
Its not as bad as it looks. The temp sensing is what may be affected... a poor GND or junk sensor.
now showing zero !!
> CEL ON:
Let's read the OBD port for fault codes with MB compatible scanner (from Amazon or directly from China) - The check engine light is on : your lucky day hopefully!
The cluster Temp display is not directly from sensor. Instead it's driven by ECU after doctoring data. The way this is swinging up/down so fast make this an electrical issue.
Try not to drive it so much under these conditions. The ECU work is affected by bad temperature input.
Last edited by CaliBenzDriver; 11-15-2023 at 03:32 AM.
Either you have a bad contact at the coolant temperature sensor connector or the sensor is failing.
Once ECM lost coolant temperature data, it will do maximum fan speed as a an emergency SOP to not overheat the engine.
Certain hot coolant temperature and then engine get shut down, can also under normal ECM SOP to do full fan speed for a while.
Agreed I'm waiting for your help I'm scanning it with an obd device. First it gave error P0483, then one day it gave error P0019. There is no P0483 error now. I went and bought a new ECT Sensor and installed it. There was no change and it still gives P0119 ECT error. Some people have gotten rid of this problem by replacing the fan module. But it is an expensive solution. I want to be sure. I'm not sure if there is a problem with the ECU or if the ECT sensor cable is faulty.
Are you talking about the engine coolant temperature sensor? Mine is in the front above the thermostat. I replaced that sensor but it didn't solve it. I don't know if there is a problem with the sensor's wiring.
Agreed I'm waiting for your help I'm scanning it with an obd device. First it gave error P0483, then one day it gave error P0019. There is no P0483 error now. I went and bought a new ECT Sensor and installed it. There was no change and it still gives P0119 ECT error. Some people have gotten rid of this problem by replacing the fan module. But it is an expensive solution. I want to be sure. I'm not sure if there is a problem with the ECU or if the ECT sensor cable is faulty.
Any chance you can get the english description of your engine fault codes to make this remotely useful?
Last edited by CaliBenzDriver; 11-15-2023 at 06:34 AM.
No, my engine is 1.8 M271 gasoline I didn't fully understand what you said:kafası karışmış: My ECT sensor appears to be on the thermostat. I only understood your last sentence. It doesn't work all the time, sometimes the fan works fine and sometimes it works problematically.
Of course, let me explain. P0483 : Engine cooling fan rationality check malfunction
P0119 : Engine Coolant Temperature Sensor 1 Circuit Intermittent/Erratic
Faults are recorded faults, not ongoing ones. But even if I delete them, they repeat
P0483 : Engine cooling fan rationality check malfunction <<<< rationality is when computer thinks the condition of the error does not make sense P0119 : Engine Coolant Temperature Sensor 1 Circuit Intermittent/Erratic <<<<<<<< see, even the DTC explain intermittent sensor
Of course both DTCs will appear again after deteletion, when and if the P0119 : Engine Coolant Temperature Sensor 1 issue is not addressed.
If your ECT sensor is new and genuine and still the DTC pops out, it could be the wiring to the sensor which is intermittent bad contact at the connector, if not the wire to it somewhere along
the wire harness is cut or wounded and short to ground.
You wrote : sometimes the fan works fine and sometimes it works problematically. As explained earlier, that is because : Once ECM lost coolant temperature data, it will do maximum fan speed as a an emergency PROCEDURE to not overheat the engine. Certain hot coolant temperature and then engine get shut down, and then turn ON again can also under normal ECM procedure to do full fan speed for a while.
Now we know your fan 10% PWM is not lost.
10% PMW signal means fan is OFF , this signal comes from the engine computer if for my M276 and would be the same for ur M271.
If wire is damage or cut, there is no signal at all, fan read it as zero % PMW or let say 100%* PWM ( *which is basically direct connection without driver pulsing a PWM signal ) both this condition will make fan go maximum speed all the time ignition key is ON.
Maximum PWM as maximum fan speed is 90%, not 100%
attached a good reading for ur engine
Last edited by S-Prihadi; 11-15-2023 at 08:26 AM.
Reason: add info
Yes, I changed that sensor, but there is no solution. I understood what you said. You explained it in detail and beautifully. Thank you. My first job right now is to find an electrician. I will check the sensor wiring. I will replace it completely if necessary. If it is not resolved again, I will start to suspect the ECU And as you said, I see 10% when the fan is not working in the car. When it works it shows 90% value. So the fan is working but there is something that is causing it to go wrong.
I can only be suspicious Mercedes uses their amazing painted GND post manufacturing on your car.
marginal GND post (inside dry cabin)
thick lip of paint... no contact!
It's a 5mn free fix to clean once you've spend the time to figure where a poor GND is disrupting this circuit.
I think we may need your VIN to pull the ECU schematic most applicable to your car.
Leave it up to MB to find the best place for its engine ECU.... in the hotest location: ECU over exhaust pipes
I don't think ECU is prime candidate here. It's on the list of suspects but not high on top. Bosch electronics are mostly robust.
Last edited by CaliBenzDriver; 11-15-2023 at 05:03 PM.
There were people who solved the problem by changing the fan in the topic I sent you below. Does the fan module affect the temperature display? Who controls this indicator? Is it just the ECT sensor?
There were people who solved the problem by changing the fan in the topic I sent you below. Does the fan module affect the temperature display? Who controls this indicator? Is it just the ECT sensor?
You're right. I will follow the values of the ETC sensor with Xentry and share them with you. Can you describe where the GND screw you mentioned above is located?
You're right.
I will follow the values of the ETC sensor with Xentry and share them with you.
Can you describe where the GND screw you mentioned above is located?
The GND shown above is at front footwell on either sides.
I recommend you stay focused on fixing gauge first without disturbing any other non-related circuits at this time. This will save you troubleshooting time.
Lets find out where the swinging temps come in: sensor, connector, harness, ECU, Bus, display ?
What your gauge circuit looks like is found on a circuit diagram we need over half a dozen ECU pages I guess...
I am not at home in Jakarta, me now in Bali.
So no ECP/WIS access from my PC to pull out the Engine computer wiring diagram for this M271.860 EVO engine
Melhaba: I return with couple ready found answers for ya!
It's unlikely a bad ECT. The ECU reads bad data that it displays. ECU believe genuinely it is overheating but is wrong. There's a voltage goof somewhere...
Yes, I tracked it yesterday with the Car scanner. The car's temperature gauge was always just above 80. However, the car scanner was reading very different values. It was constantly changing. Towards the end, as I parked the car, the car scanner was reading the coolant temperature between 83 and 90, and the vehicle's temperature gauge read 0. It suddenly dropped. But the car scanner program never showed 0. The fan turned on when the car's temperature gauge reached 0. After a few seconds the indicator returned. It returned to normal and the fan turned off.
I guess the ECU does not control the car's temperature display. Because it shows different values with the OBD device and the cars indicator is 0, but the OBD device does not read 0.
Yes, I tracked it yesterday with the Car scanner. The car's temperature gauge was always just above 80. However, the car scanner was reading very different values. It was constantly changing. Towards the end, as I parked the car, the car scanner was reading the coolant temperature between 83 and 90, and the vehicle's temperature gauge read 0. It suddenly dropped. But the car scanner program never showed 0. The fan turned on when the car's temperature gauge reached 0. After a few seconds the indicator returned. It returned to normal and the fan turned off.
I guess the ECU does not control the car's temperature display. Because it shows different values with the OBD device and the cars indicator is 0, but the OBD device does not read 0.
That's odd because ECU 100% controls the IC gauge displaynfrom what the ECT sensor says.
In your case you report ECT OBDII data stays reasonable but gauge goes wild.
Question is how can that be ?
-- Are Coms from IC Display to ECU disrupted ?
-- It seems to be chaos between ECU <---> IC.
Any other fault evidence of that??
Even though ECT display on gauge of Instrument Cluster is via CAN BUS from ECM to Instrument Cluster, this digital data is still intepreted mechanically to the looks-like-analog gauge needle...correct ?
Yes, It is not a true mechanical as say an old bourdon tube, but it is not true digital as in display like S class of say W220 era.
Here, they even sell the gauge pointer needle of W212: https://www.ebay.com/itm/285100681658
So that means there is some sort of small servo motor doing the mechanical action for this needle.
I am not at home in Jakarta, me now in Bali.
So no ECP/WIS access from my PC to pull out the Engine computer wiring diagram for this M271.860 EVO engine
Yes, when I check with the OBD device, the data never drops. But the car's indicator sometimes drops. I think that if there is a problem in the brain, the OBD device should also give wrong data. A wrong signal is coming to the car's display. But if the brain reads the ECT sensor correctly and the sensor does not show any abnormalities, why is the fan running? I'm going to the electrician tomorrow. I'll tell him and see what he says
11-14-2023, 06:10 PM
W212 E250 Engine Coolant Temperature Fluctuation
I'm waiting for your help 
I'm scanning it with an obd device. First it gave error P0483, then one day it gave error P0019. There is no P0483 error now. I went and bought a new ECT Sensor and installed it. There was no change and it still gives P0119 ECT error. Some people have gotten rid of this problem by replacing the fan module. But it is an expensive solution. I want to be sure. I'm not sure if there is a problem with the ECU or if the ECT sensor cable is faulty.
damn, my brain haywired today hahahah.
And as you said, I see 10% when the fan is not working in the car. When it works it shows 90% value. So the fan is working but there is something that is causing it to go wrong.
