Apologies for the long story for context.

Pierre needed to be parked up after a water leak (sunroof drains blocked). Everything was fine apart from the small lake in the rear footwell... so we had the carpet out, left it to dry out with the rice and newspaper etc.
While it was parked, I disconnected the battery to keep the immobiliser from draining it.

Some weeks later it's all back together, so I charge up the battery (which didn't take more than 20m) and I went to start the car.

1999-era Meganes are peculiar in that to disarm the immobiliser after a battery-off job, you need to remote-lock the car using the blipper on the key, then remote-unlock it. This process makes the immobiliser know the entry is kosher and it's all good to start. I've done this loads of times over the years and it's always been cool.

Anyhow, on this occasion the C/Locking blipper doesn't lock the car, or unlock it, so the immobiliser rightly won't let the car start.

My first thought was that the car battery was maybe flat, even though the charger said it was good.... but the engine turns over fine (the immobiliser disables the fuel pump so the car still cranks, but doesn't start).

Next idea was locking the car using the key in the door lock... even though only remote-locking/unlocking with the blipper is going to release the immobiliser. I tried it anyway... but (rightly) it didn't work.

Next idea was maybe the key is duff, so I gets the spare key. The regular key is RF (not the earlier Infra-Red)... and has an LED that lights up when it transmits. That looks fine.. but I also tried the spare key. The spare key has an LED but it didn't light up.. so the spare key battery was obviously flat. I replaced the battery in the spare key and now both keys light up their LEDs... and both keys still don't remote-lock/unlock the C/Locking, so at least they're consistent.

Now Pierre has lost its key-to-immobiliser "synchronisation" in the past... in winter when the battery died, but the C/Locking would always work, even if the immobiliser didn't recognise the key itself (in the ignition)... so the immediate problem is not key to immobiliser synchronisation.

The C/Locking itself works fine using the button inside the car, so mechanically it works. It just doesn't activate when blipped using the key.

So, either the C/Locking receiver (wherever that is) is not getting the signal (could be a key-code to CL module issue, or it could be a simple receiver issue) OR it's getting the signal but it's not talking to the C/Locking actuators.

I've dismantled the headlining looking for a receiver (cars with IR have the receiver in there, but Pierre has an RF system)... and around the fuse board and the Body Computer doodah .. and it all looks in good order.. no blown fuses, or signs of water ingress, never mind any corrosion or damage.

Is there a way to reset/synchronise the RF key to the C/Locking? The key can be synched to the immobiliser by holding the button pressed for 10 seconds till the LED light goes out and then double pressing it... but that's key vs immobiliser, not key vs C/Locking.

Otherwise where is the RF signal receiver unit? How can I tell whether it's receiving?

TIA.

Edited by Mino on 25/07/2023 at 12:06