Citroen DS3 P0335 no start

[justinzak]

Hi there, have a headache of a problem with a citron DS3 1.6 hdi 2014.

Crank no start, P0335, no signal from crankshaft sensor. On live data, no rpm is read from the crank.

Probing the wires, according to the diagrams it is ;
1- 5V supply
2- signal
3-ground

This was all correct at the sensor, with the signal wire having a 5v reference. ECU is a sid807evo, with all the crank wires being on row 2 of the grey 48 pin connector.

Car has had two replacement crank sensors, one aftermarket and one genuine. Reluctor ring has also been changed, and a spare ECU tested to see if it can read crank signal.

On the oscilloscope, there indeed is no signal coming from the crank sensor. It does pulse, but the amplitude is only maybe .5v and with little coherence. It was tested both on the vehicle and off, with a drill turning the old reluctor ring. When the sensor is plugged in, the voltage on the signal wire drops to about .7 volts, I assume this is fine? Also ran wires directly from ECU to the crank sensor using OEM pins in heatshrink.

Really have no more ideas left!!

(Waveform on screen is just a sample)

[wheeler]

Something aint right here. I'd say you checks are very thorough. The big question is what is the history of this car & the fault? Was it running ok one day then not the next? Was it bought as a non runner? really need more info.

[justinzak]

It was a breakdown I believe, that got sent to a mechanic on warranty. The warranty company refused to pay the rate the mechanic was charging however, and so the car has been passed on to this shop in an unknown state. Crank sensor, timing belt, and reluctor ring were replaced at this shop, after which I was called in for assistance. Only signs of potential foul play were a snipped wire inside an ecu plug cover.

There only other fault code is a starter line fault P1694 which I believe is triggered by absence of crank signal.

[wheeler]

Ahh, i see. I’d bet any money that your not getting the full story here.
If this was just a simple breakdown & no one is telling you lies/not giving you the full story i can’t really see what else you could check.
Have you replaced the terminals at the ECU side?

[justinzak]

Considering im getting 5v,5v and gnd on the sensor wires I've made the assumption that the ECU plugs are okay

[justinzak]

I decided to bench test a couple of the sensors. What is found is that when I rotate the reluctor ring Infront of it, I get a slight waveform with peaks of 4.3V and 4.8V, about 500mV amplitude. If I place a magnet Infront, I can make it demonstrate a full 0-5V signal.

[justinzak]

Weirdly, after hitting the crank sensor with the magnet, the voltage changed and i tried the reluctor ring on the drill again, and managed this waveform. Im unsure about the noise, but it seems to be working now.

[justinzak]

I may be spamming my own thread, but this information may help someone in the future. I've come to a couple conclusions,
- I've got at least one bad crank sensor.
- The crank sprocket on the vehicle does not produce a waveform on the scope, but when I rotate the old sprocket next to it, it does.
- Even with a nice waveform, I don't get any rpm reading on the cluster or diagnostic tool - on both ECUs. I'm going to make the risky assumption that it requires either a cam sync, or running motor (ie starter motor not engaged) to produce an rpm reading.

Based on the P0335, and the scope data showing no waveform for the sprocket on the vehicle, I'm going to make the call that the new sprocket is faulty and the old one must go on. I see this as the only possibility - and that's putting trust in the scope data. The sensor was not very picky about the air gap or placement with the spare sprocket.

My rudimentary test setup;

[citroenguy]

Interesting case you've got there!
Will follow the outcome

//A fellow diagnostics-mechanic

[justinzak]

Just returning to confirm it was indeed a faulty crankshaft sprocket. There is nothing visually wrong with the sprocket, but I noticed that it's not magnetic. I guess that's the problem with non-genuine parts. It was bought form a napa/motor factors place.

[wheeler]

Cant say ive ever seen one of these reluctor rings fail unless its had physical damage or debris. You reckon the original failed & also the new aftermarket one was dodgy?
What's the chances?