2008 C5 BHI wiring

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Ggkiwi25
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Joined: 26 May 2020, 03:41

2008 C5 BHI wiring

Unread post by Ggkiwi25 »

Does anyone out there have aN electrical wiring schematic for the BHI suspension Hydraulic pump circuit for a 2008 C5 HDV6 .
Hoping to track down a fault with the pump not running.
I suspect the LDS have leaked into the motor housing and contaminated the brushes, but want to trace the circuit before removing the BHI unit.

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GiveMeABreak
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Re: 2008 C5 BHI wiring

Unread post by GiveMeABreak »

Can you confirm exactly what model you do have; your profile says a 2006 C5 (MK II) and you are talking about a C5 2008 (MK III or X7)?

In any case, it is likely to be the main fuse is blown if it is not operating. Probably as a result of overheating - possibly due to the internal contamination of LDS into motor as you have mentioned. There is no internal schematic of the BHI.

Once we know exactly what you have (a VIN would be better to be honest) we can advise on fuse location.

Ggkiwi25
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Re: 2008 C5 BHI wiring

Unread post by Ggkiwi25 »

Hi Marc
I’m not sure why my profile has a 2006 C5, I don’t think I had actually filled in that field, I’ve updated my profile now.
The cars VIN is VF7**************[VIN obfuscated, can be read by forum staff].
I’m hoping I can track down wiring diagram (for this model car) to see the current path to the BHI unit, I know there’s a fuse in the passenger compartment G39 fuse box B and I’ve mentioned I’ve found a blown 40A Maxi fuse in the engine compartment (which doesn’t seem to coincide with any of the diagrams I’ve found online so far) , I’m keen to understand the control circuit/harness layout and check that out before disconnecting the hydraulics BHI etc.
I had purchased a online Haynes manual, but am disappointed that it doesn’t have any reference to the suspension electrics.
Do you know if there’s a relay for the pump motor remote from the BHI unit or is it part of the unit?.
Any help you can provide would be much appreciated .

Thanks

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GiveMeABreak
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Re: 2008 C5 BHI wiring

Unread post by GiveMeABreak »

I'll put something up for you tomorrow as these vary depending on system, but now i have your VIN I can determine the correct one.

Ggkiwi25
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Re: 2008 C5 BHI wiring

Unread post by Ggkiwi25 »

Thanks Marc
That would be great

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GiveMeABreak
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Re: 2008 C5 BHI wiring

Unread post by GiveMeABreak »

So you have the 2.7 DT17TED4 engine, which in common with the 3.0 HDi has a different suspension control system. It uses a separate Suspension ECU as found on the C6, different from the 4 cylinder models that use the ECO Suspension ECU incorporated in the BHI.

However, the AMVAR function that used on the C6 that controls the damping at each strut was not implemented on the C5 X7, so be aware of this. It means that you will have 4 height sensors (one on each wheel), as opposed to 2 (one on each axle) on the 4 cylinder models.

The functionality is the same, but the data from the height correctors is analysed and calculated differently by the separate suspension ECU.

7751-4 are the height sensors (the dot on the house symbol shows which wheel)
1524: Supply cut-off relay
7758: Variable damping ECU (without variable damping function as I said above)

Fuse G39 is in the BFH1 fusebox where the BSI is in the passenger glovebox (but be aware there are 2 sets of 'G' fuses!) You need the bank G36-G40. It may be tucked to the
side somewhere attached to the BSI. Also be aware that some X7 Owner's Manuals had the incorrect fuse information, typically showing Fuse Box 'A', 2 Fuse Box Bs and NO fuse box 'C'. I've arrowed in green the 2 G39 fuses, you need the one in Fusebox B which is a 10Amp for the Suspension.

There is also Fuse F13 in the BSI (Hydraulic suspension pump cut-off relay)
Maxi Fuse MF7 is for the active suspension with variable damping (may be there for operation of the system, but without active damping)
Maxi Fuse MF3 is for the Power Steering
X7 Susp Fuses.PNG
Image

Ggkiwi25
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Re: 2008 C5 BHI wiring

Unread post by Ggkiwi25 »

Thanks Marc
That’s very helpful.
Is the a wire colour reference available for these diagrams?
I see there is also the front/rear axle sensors shown (7746/7747)on the diagram and a seperate control module 7715, is this used as well as the 7758 module or is it redundant on this model. It appears that the G39 fuse is for this module (7715) supply?
I also traced the diagram back from the pump motor 7739 and it appears on this diagram to be supplied by MF 3 (which makes sense as this is the blown fuse and the power steering seems to work fine)
Do you have a wiring diagram you could post for the power steering circuit and electro valve circuits? I’m interested in fully understanding the electrical control circuit.
Is the 1524 relay located on the BHI or seperate on the BSI .
The car is located 100km away and as it’s sitting right down on the stops it can’t be driven very far, I’m hoping to get a chance to get back to it later this week.
Everything is pointing to a contaminated pump motor I think , but I’m keen to have all the info before I drive back up to diagnose and confirm I need to pull the pump out.
Thanks again for your help with this.

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GiveMeABreak
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Re: 2008 C5 BHI wiring

Unread post by GiveMeABreak »

1) 7715 is the suspension ECU incorporated on the BHI and this does the controlling of the BHI and electrovalves on all models.
2) 7758 Is the additional CSS Suspension ECU only found on 6 Cylinder engines like yours. Its function on the C5 X7 is dedicated to the vehicle height sensors and the power steering.
3) I think you mean 7748 and 7747 ion the diagram (not 7746). These are the front and rear suspension electrovalves. Don't get these confused with height sensors on the front and rear axles of 4 cylinder models. 6 Cylinder C5s don't have axles height sensors.
4) Yes G39 is the main fuse for the Hydraulic suspension / Pump

Power Steering Diagram

Image

5) The relay is located near the suspension BHI - the only diagram I have is here:
1524.PNG
1524.PNG (19.98 KiB) Viewed 64 times
If the pump isn't running, change the fuse G39 - and see if you can get the pump running enough to get it off the ground. Once up and pressurised, the motor only really runs occasionally to maintain pressure - the pump does not run all the time unlike older days of the CX Hydropneumatic systems.

Ggkiwi25
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Joined: 26 May 2020, 03:41

Re: 2008 C5 BHI wiring

Unread post by Ggkiwi25 »

Thanks Marc
This is great, thanks for explaining the electro valve/sensor arrangements
I’ll get back up to the car next week and check the wiring out based on your info.
I’m pretty sure it’s LDS in the pump motor at this stage though, hopefully it’s not too far gone that a clean and re assemble won’t fix!.

Ggkiwi25
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Joined: 26 May 2020, 03:41

Re: 2008 C5 BHI wiring

Unread post by Ggkiwi25 »

Hi Marc
Managed to get BHI unit out yesterday and sure enough a fair bit of LDS and carbon paste build up inside.
50DF7E93-C4FE-41D5-B621-8B5737F4EDA7.jpeg
I forgot to size the high pressure blue o-rings, do you happen to have a spec for these (size/material) ?

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GiveMeABreak
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Re: 2008 C5 BHI wiring

Unread post by GiveMeABreak »

And it looks like one of the wires has sheared off where I have highlighted it in green... so that will be why the pump isn't working....
LDs Wire.png