Weird Electrical problems - New Owner C5 X7

[GiveMeABreak]

The horn is Fuse F2 in the engine compartment Fuse Box, protected by a 15 Amp Fuse.

[deaconj999]

Did you also put the original harness back in and reset the BSI before trying?

Re the brightness control - that's not on the steering wheel controls, it's on the speedo here at 'F' - you hold it until the desired brightness is reached, then it goes the other way.:
Dash Lighting Control.PNG

Here's the location of the Horn:

X7 Horn.PNG

Got it thanks, No I didn't do a BSI reset but will do tomorrow. I mistakenly meant the steering control no 10 LHS to dim but I remember it reverses the centre console small display if you want.

[deaconj999]

Hi Guys,

Latest to this horn problem it that a BSI reset has been performed and the horn is not working. The user manual doesn't show how to reprogramme the tyre pressure sensors either. How does this work it used to be green lines now Red.

Check button shows nothing as before so no problems.

I followed the BSI procedure:

Battery Disconnect / Reconnect Procedure

Thanks in advance.

[GiveMeABreak]

The TPMS shouldn't need re-programming under normal conditions - unless changing the Sensor itself. Check again after you have driven a few miles, by pressing the CHECK button and then seeing what they say.

If the system is faulty, it will tell you the tyres are not being monitored and display a warning. You can't programme these yourself - they have to be done with a Lexia and an 'Exciter' or similar tool, which the dealer can do (unless you have the kit of course). Again, I would wait until you have driven about a bit and then check the system. It may take a little while to stabilise and report the pressure status.

[deaconj999]

The TPMS shouldn't need re-programming under normal conditions - unless changing the Sensor itself. Check again after you have driven a few miles, by pressing the CHECK button and then seeing what they say.

If the system is faulty, it will tell you the tyres are not being monitored and display a warning. You can't programme these yourself - they have to be done with a Lexia and an 'Exciter' or similar tool, which the dealer can do (unless you have the kit of course). Again, I would wait until you have driven about a bit and then check the system. It may take a little while to stabilise and report the pressure status.

Thanks Marc, your knowledge and fast responses are invaluable.

I thought it might be a case of the movement of the sensor that would activate them. Now the horn. I have done what this forum has advised and I did the BSI with the old radio, the horn didn't work. I then did the same with the new radio. Remember the horn was intermittent after the install. ODDEST thing here, I was wrapping up and thought I'd test the alarm as the last check, having done all the other, lights reversing aids and sounder etc. All work fine. HOWEVER, I put the key in the door and turned it left and then unlocked the car I opened the door and reached in and the HORN WORKED repatedly on both buttons. I then closed the door locked it with the button on the fob and then reopened it and the horn didn't work. What the heck!!! That's thrown me another curve ball as I was getting to the point that I thought the horn was u/s and it obviously is not. I'm flummoxed!!!!!!

[GiveMeABreak]

I can only suggest that it is obviously not happy. Something, electrical most likely, may be interfering with the system. This is just the sort of thing I was trying to explain in an earlier post about multiplexing. Did you get round to replacing the wiring connecting block / harness with the original one when you put the old head unit back in?

[deaconj999]

I can only suggest that it is obviously not happy. Something, electrical most likely, may be interfering with the system. This is just the sort of thing I was trying to explain in an earlier post about multiplexing. Did you get round to replacing the wiring connecting block / harness with the original one when you put the old head unit back in?

No, I used the one that the Supplier sent me INCAREMPOREUM. But I just got back from a little spin. The tyre sensors are fine as suggested. The horn has now decided to work again on the way back. Th eonly adde dthing I di on the spin out was to stop and reset the clock on the dash with the steering wheel buttons and kept the mute button in to check the radio head unit (Pioneer) would mute. All with the engine running, pulled off about 300m and tested the horn randomly and it has worked every time I pressed it. Neighbours giving me funny looks LOL.
I probably still need to get it on a Lexia or buy one!

[GiveMeABreak]

Ok, so just keep an eye on things, but if the ejector seat launches you into outer space tomorrow, you know you've still got a problem

[deaconj999]

Ok, so just keep an eye on things, but if the ejector seat launches you into outer space tomorrow, you know you've still got a problem

Don't tell me the airbag doubles as a parachute on a C5 lol

[deaconj999]

UPdate - the horn issue was a faulty horn which has now been replaced, the guys at the garage didn't specify the exact fault when I asked so I believe it may have been corroded contacts on the horn rather than a faulty wire.