Crankshaft position sensor doesn't respond

[Martín Rodríguez]

I have a G4+Force GDI connected to a Ford Ecoboost 2.3 L. It was working without any problems during more than a year but suddenly it started to fail, the strangest thing is that the problem happens randomly. I think the cause of the problem is the signal of the crankshaft prosition sensor, sometimes the pulse signal is correct and the engine starts and sometimes it only has 4 V without any change so that the engine does not starts (I’ve captured the trigger of that sensor and also measured it with the multimeter). I've changed the sensor, the connector, inspected the wiring and even the pin on the ECU connector, nevertheless I have still the problem. 

I wonder if you could help me with this.

Many thanks

[Adamw]

I think if you are seeing the same constant 4V with a voltmeter then we can at least rule out an internal ecu problem.

The 4V at the ecu pin or showing in the trigger scope is due to the internal pull-up resistor.  The crank sensor effectively connects the trigger pin to ground when a tooth goes past the sensor to give you a signal that switches between 0V & 4V.  So, when you have constant 4V at the ecu it suggests the sensor is not grounding this pin when it is meant to.  So it could be a bad ground wire to the sensor, a failed sensor, a bad signal wire between ECU and sensor, or the power supply to the sensor is missing.

Some quick tests you can do next time you have the problem to eliminate some of these possibilities:  Unplug the crank sensor and connect the signal pin to ground with a small piece of wire or similar, if you then see constant 0V in the trigger scope then that would mean the signal wire is ok.  Next you could loop the ground pin to the signal pin in the crank sensor plug, if you still have constant 0V in the trigger scope then that would confirm the ground wire is ok.  Then check the power supply pin with a voltmeter.  If all of those tests look ok then it would suggest the sensor is failing or not switching for some other reason such as air gap or magnetised wheel etc.