C5 front height sensor on the way out?

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Lenny
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C5 front height sensor on the way out?

Unread post by Lenny »

Good evening all,

I've had a brief flash of 'suspension fault' pop up on two occasions over the last month or so and on both occasions the nearside front wheel was splashing through standing water.
The message disappears after a couple of seconds and all is fine with how the car drives.
I've plugged the old laptop in tonight and there were the following codes recorded in the suspension:
U1118, U1118 (yes, same code twice), U2118, C1142 & U2005 (which I understand is irrelevant).

I've cleared the faults, been for a drive, and the only one that came back was U2005 (which is irrelevant :) )

C1142 is 'front body height sensor fault' so my thinking is that the sensor is on it's way out.

Anybody been through similar?

(C5 X7 Exclusive auto 2010)
PaulC5
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Re: C5 front height sensor on the way out?

Unread post by PaulC5 »

Not had this fault. The sensor pivots can break and occasionally I grease the ball joints on them so they move freely.
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GiveMeABreak
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Re: C5 front height sensor on the way out?

Unread post by GiveMeABreak »

The U codes are generic and can relate to any system and mean there is a communication fault, so no good without the ECU to which it relates.

U2005 can be ignored as it relates to a speed fault when the suspension ECU is being diagnosed.

The key fault is C1142 that relates to the Font Body Height Sensor, meaning open circuit or short circuit to earth. Probably as a result of the water, being that it sits at the corner of the left front wheel near the front anti-roll bar. So likely water has gotten into the unit or the connector and is causing intermittent issue. This will need attention at some point as it may become a persistent problem and need replacing. Just don't get underneath the vehicle in any case unless it's independently supported and it is well-known these can drop instantly to the ground when there are issues with the height correctors.
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Marc
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Lenny
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Re: C5 front height sensor on the way out?

Unread post by Lenny »

Thanks very much.
I've ordered a new, genuine sensor (local dealer was cheaper than Ebay) so hopefully I'll have a look at it over the weekend.

I was surprised to see that cheapo ching-chong pattern parts were available but decided it wasn't worth the risk. Replacement doesn't exactly look like a ten minute job if a cheapo part turned out to be faulty.
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GiveMeABreak
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Re: C5 front height sensor on the way out?

Unread post by GiveMeABreak »

Just remember not to remove the bracket - leave this in place as it's set and positioned correctly for you to replace the sensor. If the mounting bracket is removed without marking exact position, the suspension heights will be wrong and the whole measuring procure will likely have to be done to set the heights again which can be a real b*ll ache.
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Marc
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Lenny
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Re: C5 front height sensor on the way out?

Unread post by Lenny »

Pleased to say that I found the problem, the cause of the problem, and fixed it without much hassle.

The problem was water ingress on the wiring plug to the sensor, causing a bit of blue corrosion to both sides of the connection...

Image
Image

...and the cause of the less that perfect seal must go back about five years or so when I got a local garage to change those rear bushes on the front lower arms.
Presumably they disconnected the sensor and somehow managed to kink the seal on the plug. The wiring was also incorrectly routed and not attaached to the bracket where it should be...

Image

My theory is that the corrosion was causing a less than perfect connection and the force of the splashing water moves the wiring slightly (due to it not being located properly on the supporting bracket) causing a very brief break and corresponding fault code logged.

I've fitted a new height sensor, cleaned the corrosion from the wiring side of the connection with contact cleaner and attached that wiring to the bracket as it should be. All connection seals had a smear of my favourite smelly waterproof grease, as well as the corrector linkage.
I cleaned any muck from behind the wheel arch liner, lathered inner wing with Waxoyl, put back together, quick BSI reset when reconnecting the battery, and all is well.

It's not a bad job to do really. Access is tight and getting the small retaining bolt back in took many attempts and several uses of every available swear word.
It'd have been a five minute job if I'd had ET's fingers :-D

Image
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GiveMeABreak
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Re: C5 front height sensor on the way out?

Unread post by GiveMeABreak »

The usual combination - the dreaded water and clumsy garage mechanics that end up causing more problems than they solve by leaving half the fixings removed or things not put back properly.

Glad you have it sorted.
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Marc