P0335 crankshaft sensor fault, struggling to diagnose

[Spindlow2]

It ran perfectly and started first time every time, until it didn’t… came back to the car after shopping to find it wouldn’t start at all, and threw a p0335.

I’ve replaced the crankshaft sensor (Citroen original part) and no improvement, was advised by RAC tech to replace pigtail connector as apparently these are a common problem. Replaced the connector, still no improvement. I even replaced that section of the loom with new wiring to eliminate any possibility of a wiring issue.

Hooked up to an oscilloscope as something seemed off and signal is perfect from sensor to the ecu. (So the reluctor ring is fine)

Then it gets odd. After about a week of no time to look at it I tried it again and it fired up, ran perfectly for about 10 mins and then cut out. Wouldn’t fire again for the next 5-10 attempts, then fired and cut out after a few seconds… wouldn’t fire again for a fair few times, the fires up and ran perfectly for about 5 mins before again cutting out.

Whilst running the sensor pattern on the scope is perfect but then just cuts out.

Fuel pressure is also fine and doesn’t drop

Any ideas? I’m running short of them!

[Spindlow2]

Forgot to add, it’s a Citroen DS3 1.6 HDi (2013)

[PaulC5]

It suggests the crank shaft sensor is faulty. Early signs of failure are they stop working when hot then once cool work again until hot. You could try blowing cold air over it to see if it lasts longer before failing. If the part is faulty so soon after buying I would think you could try taking it back to your Citroen dealer for an exchange (assuming by Citroen original part you mean it was bought from a Citroen dealer).

[Spindlow2]

I’ve tried 2, plus the original… no luck at all… it feels like there’s an intermittent fault somewhere else causing this error to be thrown.

It doesn’t seem to make any difference whether it’s cold or warm. Usually won’t start at all then occasionally fires up

[RichardW]

Need to check for 5V reference and earth at the sensor, whilst giving the wiring a good wiggle to see if there is a fault somewhere.

[Spindlow2]

I’ve done this and have 5v, ground and a good signal back to the ECU. I’ve even replaced the wiring from the ECU to the sensor to ensure there couldn’t be an intermittent break on the cables still no luck

[PaulC5]

Where did you get the sensors from, was it a Citroen dealer ?

[Spindlow2]

Yeah, main dealer parts used, as I say I’m at the point of the sensor is DEFINITELY not the problem, neither is the wiring (replaced the entire length of wiring from sensor to ECU) or reluctor ring (perfect scope pattern), hence my confusion.

As you can see in the pic of the scope it’s signal is perfect (measured next to the ECU between ECU ground and sensor signal)

I’ve replaced the wiring just to rule out intermittent faults too

I’m now considering a BSM problem or ECU issue but unsure how to proceed in testing further.

The fault is not effected by heat or vibration near the sensor so I’m thinking maybe voltage being cut by a relay in the BSM if it is failing (this was suggested by AI which I reluctant to trust but now out of ideas)

Apparently this fault can be thrown if the engine is stopped due to being cut out by loss of voltage to the sensor.

My only other thought is an intermittent ground, but that wouldn’t make sense with a perfect oscilloscope readout unless it’s being disconnected suddenly and pretty completely?

Really stuck for ideas.

[PaulC5]

Something to read but it might not help as you are getting a signal on your scope. https://www.aussiefrogs.com/forum/index ... ed.140880/

Another topic which turned out the crank shaft pulley was faulty (not magnetic) but again you are getting a signal on your scope so might not help viewtopic.php?t=74190

This topic suggests MAP or MAF sensors could cause the code so you could look at live data from them but the topic is not completed so no idea what the cause was https://www.peugeotforums.com/threads/4 ... um=organic

[RichardW]

Does the fault come straight back if you clear it? Do you get a read out of engine speed in live data when cranking it?

[Spindlow2]

Cheers Paul, fuel pressure is running at a solid 330000kpa so I don’t think it’s that. The second one I’ve already read but I agree, that is a different issue.

One thing I have noticed just when reviewing some oscilloscope footage is just before it died of the sensor data dropped by a couple of volts… makes me wonder further about the ground to the ECU that it then uses for reference… would this ring true to you as a likely possibility?

Do we know the location of that ground as I haven’t got a workshop manual or wiring diagram? (The first post wouldn’t let me view the wiring diagram within their post)

I’ve attached a pic of where the signal got messy just before cutting out

[Spindlow2]

Hi Richard, this ECU gives no readouts from live data until the car starts. Another member found the same when he had a similar problem (turned out to be a non magnetic reluctor ring). Once started live data is fine. This thread is also
Referenced above

Fault only returns after cranking, stays cleared until
It reoccurs.

[Spindlow2]

Still looking for suggestions if anyone has any others?