307SW (CAN) misbehaving and I'm unable to help

[HelioMV]

TL;DR - Intermittent self-locking, no crank and apparent BSI/immobiliser fault

Hi all, the golden child has started misbehaving, and I'm not able to help for a while!

Looking for some ideas TU5 307SW CAN. Unfortunately I'm away at sea for another week, so I'm working from my dad's description of what happened.

The car has recently started randomly locking itself. On one occasion it was left running while my dad got out to say goodbye to someone and it locked itself with the key still inside. They had to go home for the spare key and unlock it manually.

It continued intermittently auto-locking at home, sometimes even relocking after pressing the unlock button and reaching through an open window.

The following day it drove normally to the local tip. Afterwards they drove to a drive-through. On approaching it, the engine either stalled or cut out by itself. It then would not restart and there was no response from the starter whatsoever.

At this point other body functions also seemed to be affected – notably they couldn't close the open electric windows. They tried a basic BSI reset procedure but it made no difference.

After sitting for quite a while and trying it periodically, it still wouldn't crank. At one stage the car was locked; opening it manually triggered the alarm. After cancelling the alarm, my dad tried the key again and it suddenly started perfectly normally.

He then drove it home without any apparent engine or gearbox problem. However, the random auto-locking behaviour is still occurring, so they don't currently trust taking the car anywhere.

The battery is supposedly fairly new and the engine normally cranks strongly. Before this incident the car had been driving very well.

One other observation: someone inspected the large fuses under the bonnet and found what appears to be oil/greasy contamination on the blades and inside the holder of the 80 A fuse beneath the main relay/fuse group. We don't know how it got there. I haven't yet been able to inspect it myself for corrosion/green deposits or heat damage.

I'm thinking the important clue is that this isn't simply an engine no-start: during the episode we had no starter operation plus loss of body functions and abnormal central locking behaviour, followed by spontaneous recovery.

My current thoughts are:

- intermittent BSI/BSM supply or earth;
- poor connection at one of the main/maxi fuses;
- BSI/BSM fault;
- door latch/lock microswitch or locking command fault, possibly separate from the no-crank;
- immobiliser/start-authorisation issue.
- Key, even?

Has anyone seen this particular combination on a 307 before? In particular, is there a known main supply, maxi-fuse connection, BSM fault or door-lock input that can cause the BSI to behave like this?

I have access to PP2000/Diagbox when I'm home, but if there's anything useful my family can safely check with a multimeter in the meantime, I'd really appreciate suggestions. They need the car while I'm away. I'm really hoping there's a solution I can present them with, failing that, I'll deal with it when I get back! Thanks all in advance

[mickthemaverick]

I don't think this post is much help but the overall story certainly suggests fault/faults in the BSM to me. I'd get its connections cleaned thoroughly and ensure there are no iffy pins in the plugs as a first step.

[HelioMV]

Ok, the truth has come out. It was an attempted start by a tired family member with the key to our 3008 that triggered this behaviour. Maybe some sort of anti theft mode? I'm glad the cause is now known.

A BSI reset apparently hasn't worked but I'll confirm, this on Monday or Tuesday. Is it worth re-syncing the keys? I wonder is something now corrupted

[Paul-R]

More an observation rather than an answer. I don't see how simply inserting the wrong key would cause a problem as it would have a blade that's cut differently and so you wouldn't be able to turn it.