Possible wiring or ECM issue

WAILMOE20

MEMBER
2010 MERCEDES BENZ E200
1.8L
4 CYL
2WD
AUTOMATIC
25,000 MILES

I had an issue of the car stalling and sometimes shutting off on me while driving
And also sometimes the Needle of the engine temperature is bouncing up and down giving unreal values.
I have an issue with three sensor, Ambient temperature sensor, Coolant temperature Sensor, crankshaft sensor.
I connected the star diagnostics tool and I had the stored faults read
1-crankshaft position sensor has a malfunction signal is not present.
2-Engine coolant temperature sensor has a sporadic value.
3-Ambient temperature sensor has a short to ground.
I replaced the sensors but the issue isn’t fixed. It seems like the sensors has an intermittent issue where they disconnect and connect again.
I am afraid it is the ground circuit of the ECM.
And I needed some advice on how to track this issue.
Note: I am an electromechanical engineer freshly graduated.

7 Replies

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

The information that you requested is in the diagrams down below. 1) check this circuit for an open 2) check this circuit for a loose wire or connector for pins that are bent, damaged, or have corrosion. Dielectric grease on connectors will also help. 3) Find the short to ground and replace fuse for this circuit. Unfortunately we do not have a listing for Mercedes Benz E200 in either one of our reference materials, so I will not be able to give you wiring diagrams for these circuits. Please go through the guides in the diagrams down below and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros

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Wednesday, July 31st, 2019 AT 7:47 AM

WAILMOE20

MEMBER
4 POSTS

Mr. Alex
I have done what you said I checked the wiring and the harness as well and I checked for wiring resistance and continuity and it all gave good readings but there was one thing.
I measured the reference voltage while the sensor is disconnected at the sensor connector end and I measured it as well at the ECM and both of the readings were 3.3V which I think is below the 5V reference voltage. I even measured the voltage using an external ground to discard faulty grounding and it seems like the ECM is giving out below spec reference voltage to the sensors.

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Monday, August 5th, 2019 AT 8:34 AM

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello again,

Yes, the sensors that use a 5 Volt reference, are designed to get a 5 Volt reference from the ECM. One thing that you might want to check id the reference return, or the negative reference wire for corrosion, or unwanted resistance at the ECM connector. This could be why you are only getting 3.3 Volts. Wait, you said you used an alternate ground. Okay, test again but this time have the negative multimeter lead connected to the battery negative terminal and get back to us with the reading please.

Thanks,
Alex
2CarPros

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Monday, August 5th, 2019 AT 11:48 PM

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