Intermittent stall, now non starter

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wheeler
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Re: Intermittent stall, now non starter

Post by wheeler »

No, the immobiliser only prevents initial starting. If you broke the head off the key off or unplugged the aerial around the ignition barrel when the engine is running the engine wont stop or run any differenty.
Once the engine has started the immobiliser has nothing else to do with the running of the engine.
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GiveMeABreak
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Re: Intermittent stall, now non starter

Post by GiveMeABreak »

It's my understanding that the engine ECU is unlocked once the handshake has taken place between the transponder chip in the Key / Fob, the BSI and the Engine ECU on engine start-up. The engine ECU locks again once the ignition is switched off. It would be dangerous for the constant handshaking to take place whilst driving for safety reasons in case there was a fault and went toes up (imagine motorway driving scenario).

So there may actually be an intermittent fault with either the transponder coil that sits around the ignition barrel that reads the signal from the chip - but I have read these 2 faults elsewhere:

Have a read through this thread, only 2 pages, but had the same 2 faults:

https://www.digital-kaos.co.uk/forums/s ... sso-please
pandalooma
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Re: Intermittent stall, now non starter

Post by pandalooma »

Well thanks again to all for the assistance.

I thought that was a bit unlikely, that the immob could cause in-motion problems.

Keys: I have a spare key, not a button type, which doesn't seem to have a battery anywhere but does crank the engine. So I don't really understand the handshaking bit. Anyway I'll have a think about it but it does look like scrap now.
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GiveMeABreak
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Re: Intermittent stall, now non starter

Post by GiveMeABreak »

On the fob the chip is inside with the electronics, but on the key only type, the chip is integrated into the plastic part. The chip gets 'energised' whenever it is placed near the transponder coil that surrounds the ignition barrel which allows the chip to provide the data, which is then sent through.
NorwegianMan
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Re: Intermittent stall, now non starter

Post by NorwegianMan »

Does your engine not have a map sensor (manifold absolute pressure sensor)? As I wrote yesterday, I had exactly the same problem with my car, and when I changed the map sensor, everything was fine.
NorwegianMan
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Re: Intermittent stall, now non starter

Post by NorwegianMan »

Strange, this thread is marked with a comment from me on September 16, but now I do not find it in the thread, so I hereby post the comment again as I think it can be of great help for the thread starter:
Does your engine not have a map sensor (manifold absolute pressure sensor)? As I wrote yesterday, I had exactly the same problem with my car, and when I changed the map sensor, everything was fine.
pandalooma
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Re: Intermittent stall, now non starter

Post by pandalooma »

Resolved: I think there were two faults - the original one was a crank sensor, the second fault was caused by me rummaging around the wiring by the OBD connector. I think I disturbed a connector related to the immobiliser system. In replacing the fuse area cove I pushed some wire bundles back in, thought I'd give it one last go on the starter and... presto! it started fine. I poked around the wiring again, just because I can't leave things alone, and the engine stopped with a "immobiliser fault" on the dash. That message appeared as soon as the engine stopped, so it looks like an immb fault can stop the engine, on this car anyway. I firmly pushed in all accessible connectors under and around that area and it starts every time now. Weird but true. Just thought I'd add this conclusion to the thread. Anyway I now have a C5 so I'll be noodling around that section of the forum soon I expect!