I'm helping a friend sort his high mileage (220k+) 2004 2.0 diesel C-Max. It has a cam sensor fault, so he replaced the sensor and the car started. Once.

I've scanned the codes with a generic bluetooth plugin and the only faults are cam sensor and glowplugs (which have been faulty since he got the car 4 years ago!)

After some fault finding/tinkering i'm sure it's actually a bad earth/ bad return to ECU fault rather than a faulty sensor.

If i unplug the sensor, wait 30 seconds, plug it back in, the car will start. Once. I can can crank, rest, crank, rest as much as i like but it won't restart, until i disconnect the cam sensor again.

The joy or modern electronics, the sensors never fully power off until you physically break the circuit.

SO i'm wondering if anybody knows the "pin out" for the three pin connector on the cam sensor, i could drop in a relay and cut the power or return line to the sensor (effectively unplugging it) when the ignition is turned off. This should hopefully let the sensor/ECU circuit initialise every time the car is turned on and mean his car starts every time.

 

OR is this a know problem and there is a particular earth cable that needs cleaning/replacing?

Thanks

12 hours ago, bigbadstevieboy said:

SO i'm wondering if anybody knows the "pin out" for the three pin connector on the cam sensor,

I am assuming this C-Max wiring is similar to the Mk2 Focus, as it is the same Ford "platform".

The wiring diagram for the Mk2 Focus is on this site:

http://www.fordownersclub.com/forums/applications/core/interface/file/attachment.php?id=42087

Extracts are attached.

I would be very surprised if this sensor stayed powered up. All the sensors & actuators I have looked at power down about 5-10 sec after ignition off. But the symptoms you describe do point to that.

Much appreciated, thanks.

Just replying to this in case somebody finds this thread after a search.

 

Our problem turned out to be moisture inside the ecu, cracked it open and there was a very clear white water mark where it had got wet and dried. Gave it a bath and a brush over with some isopropyl alcohol and it's starting perfectly now. Happy days :)

 

Being able to plug in a computer and get all the problems read out for you only works if the part you are plugging into works properly itself! :)