Ford Focus 1.0L M1DA engine Crankshaft sensor fault code and injectors dropping out intermittently

RYM6746 · Post by **RYM6746** » Wed Feb 28, 2024 9:49 pm

Hi guys need your help with this one. It randomly logs a crankshaft sensor fault ( you can see it if you zoom in on the crankshaft sensor signal in line with the spikes on the math's channel in black in the file named crank vs cam). It has had a genuine ford sensor which made no difference. If you look closely at the injector firing and in line with the dips in the math's channel in black, you can see intermittently it misses turning the injector on. It has also had 3 new coil packs and 3 new spark plugs with no change at all. I have also scoped the voltage from the main relay at the ECU and the current draw at the ECU main relay it has good voltage and other than seeing the injectors stop firing intermittently it shows no diagnostic value (I THINK you may see something I'm not) in the file named crank and injector cut, This capture has an interesting characteristic where the crank sensor fault was frequent with no injectors cutting out then the engine gets switched off and instantly restarted the injectors are then cutting out frequently and the crank sensor fault is far less frequent. Obviously I need to check all powers and grounds when fault occurs but I highly doubt I'm going to find a fault on that side of it given the symptoms so I was wondering if anyone had any further testing idea's. Thank you for help in advance

Rfmotors1 · Post by **Rfmotors1** » Thu Feb 29, 2024 4:59 am

Hi RYM6746,
Here is my possible explanation for your problem.
See the spikes on orange math channel for crank sensor signal. each spike represents the sensor signal fault. The signal voltage is dropping low and this is interpreted as another count for engine speed by ECM. it also does not match the 60-2 encoder ring on crankshaft and the ECU just cannot decide when to make action to fire injectors etc. At the same time the ECU see sudden increase in engine speed so after each false crank count the engine trying to lower the rpm. I believe this is not encoder ring problem but more likely bad power supply for crankshaft sensor. From the pattern I see it looks like bad contact on sensor socket, like loose pin, most likely caused by multimeter needle pushed to connector terminal. (If this would be power supply problem to ecu, the voltage would not drop such sharply. Below is a picture with detailed points where the signal is malfunction.

Ford_Focus_2013_Petrol_Crank vs cam injector fault occured b.psdata: (16.41 MiB) Downloaded 23 times

Let me know if I have misleaded you or my explanation was correct.
Regards,
Roman

RYM6746 · Post by **RYM6746** » Thu Feb 29, 2024 9:26 am

Hi Roman thanks for your reply but since the last post I have noticed a pattern which is in an earlier capture (uploading in this post) This is too much of a coincidence to ignore. In this capture every time the crank just passes its maximum velocity seen in the upwards hump on the math's channel the fault occurs (not forgetting this is a 3 cylinder) The crank speed increases 3 times with no fault then the next 3 we have a fault again and so on. This in my mind has to be related to the rotation or the crank speed. Its just to uniform to ignore and eliminates ant wiring/pin issues. Any help with this is much appreciated Thanks again

Rfmotors1 · Post by **Rfmotors1** » Thu Feb 29, 2024 1:57 pm

If it is loose pin, it will be related to vibration which will be related to combustions and especially when misfires appears, it should get worse as the vibration got worse.
I don't have another idea.
Best to do is use the same type male terminal and make terminals tightness test at sensor socket.
It could be also the 5v reff voltage sensor supply vibrating to earth, causing intermittent short times shortcuts. This you would prove true or false by monitoring all 3 wires on the sensor socket.
Regards,
Roman

RYM6746 · Post by **RYM6746** » Thu Feb 29, 2024 3:28 pm

Hi Roman, Thanks for your help but thinking back I have scoped power and grounds at sensor when fault occurs using breakout leads it made no difference to the fault at all. Unfortunately I think that completely eliminates that theory. The fault is to much in unison with the engine but I am unable to determine the cause. Thanks again

Rfmotors1 · Post by **Rfmotors1** » Thu Feb 29, 2024 3:37 pm

OK, if you have used break out leeds at sensor side, recorded all 3 wires, then it's not at the sensor connector side for sure.
It just the pattern matched cases I had in the past.

Regards,
Roman

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