Possible wiring or ECM issue

2010 MERCEDES BENZ E200

25,000 MILES • 1.8L • 4 CYL • 2WD • AUTOMATIC

WAILMOE20

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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.

Jul 30, 2019 at 5:20 AM

SCGRANTURISMO

CERTIFIED EXPERT
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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Jul 31, 2019 at 7:47 AM

WAILMOE20

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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.

Aug 5, 2019 at 8:34 AM

SCGRANTURISMO

CERTIFIED EXPERT
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

Aug 5, 2019 at 11:48 PM

WAILMOE20

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I have done what you said Mr.Alex but it gave the same reading 3.3v.

Aug 6, 2019 at 1:05 AM

SCGRANTURISMO

CERTIFIED EXPERT
4,897 POSTS

Hello again,

Where are measuring the 5 Volt reference at?

Thanks,
Alex
2Carpros

Aug 6, 2019 at 4:45 AM

WAILMOE20

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Both at the connector of the sensor and at the ECM supply pins. I checked before the wire of the sensor and at the end of the wire. The ECM is the one supplying 3.3v. Do you think that there is a problem with ECM 12v power supply or it may be the ECM itself?

Aug 6, 2019 at 11:53 AM

SCGRANTURISMO

CERTIFIED EXPERT
4,897 POSTS

Hello again,

I would check the connector at the PCM and make sure there is no corrosion on the 5V reference pin. Other than that we don't have a listing in either one of our reference guides for your vehicle, so I can't offer any more advice.

Thanks,
Alex
2CarPros

Aug 6, 2019 at 3:39 PM