C5 V6 ES9A Camshaft Position Unknown

[stoilg]

Hi Folks,

I've recently bought a lovely C5-II 3.0 v6 petrol Carlsson Edition with some issues for a good price. Most of them are already fixed, however I am still struggling with a mystery.
The car came with engine check light on and the recorded error was P0344. Brought the car to a shop for complete aux and timing set replacement, and put brand new VTC pulleys as well, as they were rattling at start. As I suspected, the timing was not correctly set and after the replacement and proper adjustment the error was gone.

However, now the engine throws another error right after start - P1335 Camshaft Position Unknown. It is not associated to any of the banks and the engine check light does not even lit.

What was checked afterwards:
- brand new OEM camshaft position sensor replaced on rear head (bank A)
- connectivity/wiring from ECU to both sensors checked - OK
- ECU connectivity test/checks - OK
- both camshafts inspected for mechanical damage - OK
- timing double checked in alternative shop - OK

The Lexia shows that:
- the variable timing electrovalves on both front and rear cylinders are in REST state.
- Camshaft position front cyl 35 deg fluctuating 36-37 on throttle (weird!), while the rear cyl shows 35 deg stable.
I assume that due to incorrect camshaft position info that ECU receives, it deactivates the VTC operation.

Now I am considering replacement of front cyl cam sensor and maybe the crank(speed) sensor just to be safe. However before spend more money in it, I'd like to hear what your opinion/advise is.

[miked]

Hello, welcome.

I know very little about V6 petrol engines. Slightly less little about fault codes. This might not help but my first thoughts:

Does the V6 have 2 identical cam sensors? If so, then if you swapped them round you could see if the fault is with the sensor or the engine.

If the crank sensor was playing up in such a way that it didn't throw a fault up of it's own, would it not affect both cam's? I seem to remember that in a diesel (HDi), the crankshaft sensor doesn't do a lot, except check the cam sensor is in sync. I assume the same applies for the V6.

[addo]

There are a few things to check, is the part going open circuit when bolted down? Can you get a reading on a scope from the sensor?

Is the "gapping" between sensor head and inducing lugs, correct within tolerance?

If you make a simple device to imitate a sensor pulse, does this allow the engine to run?

[stoilg]

Hi guys, thanks for the prompt response.

@ milked, yes It does have identical sensors, however the rear one is located beneath the intake manifold and its tough job to remove it. This is the one I replaced with brand new, so no doubts in it.
I am no quite sure what the crank sensor does, but I've got the same info from various sources.

@ addo, these are good suggestions, but I need to bring the car to electrician to check them. No sure if there is anyone around who can test them with oscilloscope.
I never measured the gap and this is a good point. Will try! Any idea how much it should be?
Unfortunately I am not skilled enough to make such device.

I've just spoken with the mechanic, who was double checking the timing and asked him to mount the front bank sensor from another car (same engine) which is available in the shop. Will know the result later.
Keep fingers crossed!

Cheers!

[stoilg]

Latest Update...

Situation remains the same, even after changing the cam sensor.
I am still getting Camshaft Position Unknown error, no warning lit, Dephaser electrovalves are in inactive state and camshaft position on rear cylinders fluctuating 35-37 degrees.

The car runs better and smoother after the timing adjustment.

I'll try to replace the crank sensor.

[Mandrake]

Have you looked at the crank sensor signal on a scope or on the Lexia in the live data (parameters measurement) section ?

On a variable valve timing system the ECU controls the cam position actuators to adjust the valve timing for each cam, however to regulate this angle to the precise desired value through negative feedback it needs to be able to measure what the current angle is.

The only way it could do this is by comparing the crank position with the individual cam positions. To do this both crank and cam sensors have to be working. If the fault is not specific to an individual bank that points more towards the crank sensor as the crank sensor is the only one that is common to all banks when trying to compute the camshaft timing. (A faulty crank sensor would make it impossible to measure any of the cam timing angles, while a cam sensor would only affect that camshaft on that bank)

Interesting fact - SOME engines with cam sensors can actually run without a working crank sensor signal! It is clearly a sub-optimal state though - the crank sensor is very high resolution which means ignition and injection timing can be very precise, and the high resolution speed measurement is also used by the misfire monitor to detect misfires, so without a working crank sensor it wouldn't be able to detect misfires, nor provide accurate timing.

If the crank sensor was not working and it was using cam sensors only as a fall back it would have to disable the variable valve timing system and leave the cam actuators in a default position - otherwise it would have no idea where the timing was. So you would lose quite a bit of power due to lack of VVT and also imprecise timing in general.

I'm surprised it wouldn't set the engine management light if the crank sensor was faulty though! Check your live sensor data to see if any rpm or crank signal is missing, although beware of substituted values as some ECU's will measure the rpm using the cam sensor if the crank signal is missing and then report that as a crank sensor derived speed when it is not.

It's best to use a Lexia rather than a generic OBD-II scantool for these kind of tests as you are less likely to see substituted sensor data.

[stoilg]

Hi Guys,

I've replaced the crank sensor with a brand new OEM one, double checked the cam sensors, if they a properly seated (one is brand new and even tried with another ones removed from working car), swapped the VTC solenoid valves (just in case) and cleaned the throttle body (irrelevant in this case but was contaminated).
Everything looks fine, however the situation remains the same.

Via Lexia I am getting P1335 Camshaft Position Unknown right after start and the engine light lit after approximately 10km driving.

To be honest I don't know where else should I look in. It pretty much sounds like bad timing adjustment. Reading the live data, the cam angle on rear bank is fluctuating (35-37 deg) while the front is stable 35deg. Looks like the front and rear intake cams are not synchronized.

I also dag into this and found Citroen manual how to adjust the timing. Seems to be a specific procedure with multiple adjustments/checks.

On Friday I have an appointment in the local Citroen dealer for another opinion, and if they suggest the same will leave the car for timing adjustment. Hopefully they do it according to the official procedure.
I can try do it myself but my garage is tight and I don't have the required tools, so I foresee a little nightmare. However I consider this as a worst case scenario.

Its relatively rare engine and the mechanics are not familiar with its specifics.

Below are the related topics I found:
http://forum.andre-citroen-club.de/show ... nt-quot-V6" onclick="window.open(this.href);return false;
http://www.carhelp.info/forums/showthread.php?t=73931" onclick="window.open(this.href);return false;

You are more than welcome to come up with ideas/suggestions.

Regards,

Stoil

[stoilg]

Hi Guys,

The issue is finally solved. The root cause -> damaged front bank intake camshaft. The tooth was broken, the mechanic tried to fix it, however the sensor still showed weird readings. Bought a brand new camshaft 0801AT and replaced it. Its working fine now.
This is caused most likely by human error.



Cheers!

[Mandrake]

Interesting to find out the real cause of the problem - I would have never guessed a broken tooth on the camshaft!

[CitroJim]

That is amazing

[DHallworth]

That's unheard of on these V6's! They're usually bullet proof!

Had someone been in there fiddling around do you know?

David.

[Stickyfinger]

..geeze

[stoilg]

They might be bullet proof but not idiot proof. [emoji2]

I suspect that the mechanic, who did the timing belt and VTC sprockets replacement damaged it. On theory if he didn't have sprocket holder tool to loose the bolt, he might have used some steel rod there to hold the cam in place resulted in broken tooth. However the car initially had some issues related to the timing P0344, so I cannot be certain who to blame. [emoji2]

[CitroJim]

They might be bullet proof but not idiot proof.

That applies to a lot of things

[stoilg]

They might be bullet proof but not idiot proof.

That applies to a lot of things

Citroens are good cars but need gentle hands and right approach. Just like a lady!