C5 X7 VTR Tourer 2L Immobiliser Fault

[completediv]

New to this issue, but my first reaction on reading the first post was a potential battery issue. When the battery voltage wavers between good and bad it tends to throw up all sorts of weird and wonderful faults and warnings so I would, as Richard suggested, make sure the car battery is good, showing 12.7+V when resting and over 14V with the alternator charging. If the battery is poor then an element of luck comes into what works and what doesn't so check that fully and all the connectors and wiring around the BMS and engine fuse box.

Hi Mick

Previously checked battery, I think ok. But as soon as it stops raining I'll put it on charge and check round engine fuse box.

As an update, I did a bodge tape up around the scuttle panel damage Saturday pm and subjected it to overnight and all day heavy rain and tonight tried the car. Remote working, car started and no faults. As the faults have previously been intermittent and inconsistent I can't say this has fixed it, but will subject the car to the prediction of continuing wet weather plus battery and engine bay checks and see what happens. If it has sorted itself I'll update the forum.

Thanks

[completediv]

New to this issue, but my first reaction on reading the first post was a potential battery issue. When the battery voltage wavers between good and bad it tends to throw up all sorts of weird and wonderful faults and warnings so I would, as Richard suggested, make sure the car battery is good, showing 12.7+V when resting and over 14V with the alternator charging. If the battery is poor then an element of luck comes into what works and what doesn't so check that fully and all the connectors and wiring around the BMS and engine fuse box.

Just an update. Car works normally now. This is a result of multiple things I think, the main one being your voltage suggestion. I bought a more accurate meter that measures to 0.1V and I was getting 12.6V at rest and high 13V's when charging. Charged battery and it ran and no subsequent faults.
As I had heard a suspicious 'phut' noise behind bulkhead when cranking I looked at scuttle panel which had cracked and gaping seals. I taped it up and made watertight.
So I think primarily voltage, secondly ingress. Thanks for the advice Mick.

One last thing - does anyone know whether scuttle panel model number is common to all C5 X7's or was there a change during model years. I've seen a post by Mark quoting 8251CY for a 2013 model, but a breaker is telling me that number won't fit a 2010 model.

Happy New Year

[ozvtr]

After entering and starting car successfully, return to fob not working and inability to start car.

Is the above statement correct? BOTH the central locking AND the immobilizer stop working AT THE SAME TIME?

The immobilizer and central locking are not interrelated. They are completely different systems. HOWEVER, there are two places where both systems are processed. One is the BSI the other is the High Frequency module.

The High Frequency module is in the COMs unit (the bit behind the steering wheel with the wiper and light stalks). The High Frequency module receives both info from the RFID chip in the key, and radio transmissions from the central locking fob. As I said, the immobilizer and central locking parts of the key are physically separated and do not rely on each other. So to have a failure of BOTH the RFID chip AND the central locking PCB in the key AT THE SAME TIME is virtually impossible! So I would eliminate the key as a failure point.

The BSI takes decoded central locking information from the HF module. It accepts the info or rejects the info. As a security protocol, if the BSI gets central locking info that is not known to the BSI, it goes into "anti scanning mode". The BSI will stop "listening" for 1 minute (60 seconds). After that minute is up, it starts "listening" again. If the BSI accepts the DATA, it locks or unlocks the doors.
The other piece of info that the BSI gets is the RFID chip data. This is decoded and sent on to the engine ECU. The BSI doesn't do anything with this data. However the engine ECU will accept or reject the data resulting in the engine running or not.
The processes that the BSI performs are extremely complicated! The BSI would either work or not work. I would find it hard to believe that the BSI would "sort-of" work in this case. So I would eliminate the BSI as a failure point.

That leaves the HF module itself as a potential failure point. If the car fails to start AND the central locking are not working, does the interior light go out when you attempt to start the car? And does the interior light come on when you remove the key? The HF module will sense ANY RFID chip near the key barrel. The interior light should come on if the ignition is turned off and the key removed. If this is not happening, the HF module is not sensing an RFID chip. And so, potentially, not working.

The other thing, as mentioned above, is the cars' battery. If you are getting strange and unexplained lights on the dash, I would get the battery load checked. The electrical system is VERY sensitive to changes in voltages. A poor main battery can cause strange behavior.