Diagbox & Lexia Different Kind of Question

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Doo
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Diagbox & Lexia Different Kind of Question

Post by Doo »

So, I contacted Citroen UK about the issue with our C4 and starting in gear... They got back to me asking about VIN, reg no and which dealer I took the car to.

Thing is, the dealer I took it to was me and my laptop! 8-[

So, if I tell em I have one of those readers are they going to tell me it's hooky or unreliable or what? I am not sure if I should just claim ignorance and say I can't recall the dealership as it was dahn saff somewhere.

Whatever, I just want some clever clogs in Citroen to perhaps clarify the role of the accumulator sphere in the piloted box.

Personally, I believe it's job is to provide the "push" that a human leg would provide while disengaging the clutch. My theory is that the car starts in 1st gear, but with the clutch disengaged. When you rev the engine, it engages and off you pop. But if the accumulator sphere is old and wheezy, it's allowing the clutch to drag in our case and the car tries to take off. However, it soon disengages and allows you to drive normally.

The reason for my thinking is that there is no faults found and I have done 3 global scans now!

So, what should I tell Citroen UK??? #-o

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GiveMeABreak
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Re: Diagbox & Lexia Different Kind of Question

Post by GiveMeABreak »

The accumulator sphere provides the hydraulic pressure for the actuators to operate the clutch and the gearbox.

Your best bet is to let them diagnose it and don't mention anything else. These systems are mega complicated and there can be lots of reasons for failure. Your version of Diagbox may have some issues that might prevent it from picking up any faults - although I can't say for sure. The dealer will have the latest versions and will pick up any fault if there is one.

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Re: Diagbox & Lexia Different Kind of Question

Post by Doo »

GiveMeABreak wrote:
29 Mar 2021, 14:02
The accumulator sphere provides the hydraulic pressure for the actuators to operate the clutch and the gearbox.

Your best bet is to let them diagnose it and don't mention anything else. These systems are mega complicated and there can be lots of reasons for failure. Your version of Diagbox may have some issues that might prevent it from picking up any faults - although I can't say for sure. The dealer will have the latest versions and will pick up any fault if there is one.
Thing is, there is no warning lights or any visual sign of a problem, and no limp home either. This car jumps at the chance to limp home. One time it chewed up it's CV boot and it started flapping. It started to tear, making the flap bigger until it ripped the ABS sensor wires out and the car went mental. Every light was on, bings, bongs, manual gears only up to 3rd gear, reduced speed, etc, etc. So surely if there was an issue it would let us know :?

That's why I think it's the sphere. It's still working, but only just. I spoke to an electrical specialist who agreed it could be the sphere, but why isn't the car flagging up a fault?

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GiveMeABreak
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Re: Diagbox & Lexia Different Kind of Question

Post by GiveMeABreak »

Limp home is not relevant here. Reduced engine power is generally instigated by the engine ECU for engine or emissions faults only - not the gear box or clutch on a piloted manual. You wouldn't expect to have a 'limp home' mode with a manual gearbox or clutch if it or the dual mass flywheel started slipping - same thing.

It would be the first time I've heard of the accumulator sphere being at fault on these piloted boxes - but not impossible of course.

As for the faults - a sphere has no electronic parts - it is purely mechanical so cannot report a fault. However if the pressure is low, it may have some sensor in the system that could detect this and report back to the piloted gearbox ECU. This is why they are a pain in the butt. Troubleshooting these can take a loft of time, but hopefully the dealer may be able to help you.

You can see the oil level on the system if you look - but this can only be physically measured and checked (and topped up if necessary) when the system is depressurised - which you need to do with Lexia / Diagbox. Essentially that would also show you if the system was pressurising or not and that would rule the accumulator out.

Try hooking it up and going into the piloted box ECU and seeing what the live data shows - that might give you some clues.

Oil reservoir at (1)
oil doo.PNG

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Doo
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Re: Diagbox & Lexia Different Kind of Question

Post by Doo »

Thanks for that. I figure the sphere would have to have a pressure sensor somewhere. Perhaps not. On the Range Rover, the sphere's wear out and the first you know about it is the ABS system motor runs for ages after a single or couple of pedal presses when normally it tales many presses.

I want to do the oil, but not wholly convinced I can get Lexia or Diag to do the right thing. If you have any tips I'm all ears....

Gotta run just now as I have another old heap to look at for a mate :-D This time it's an Aixam. French, but running a Kubota 2 cylinder diesel engine.

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Re: Diagbox & Lexia Different Kind of Question

Post by GiveMeABreak »

As far as I’m aware the system needs to be de-pressurised and depressurised using the diagnostic system. It is essential to ensure the oil level is correct, so is only checked when depressurised.

The ABS system on PSA cars and nothing to do with the piloted gearbox system on this car for info.