How the security system works

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My Name: Ozvtr

Posts: 1197
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Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
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Hmm an interesting development.

I had cause to replace the COM2000 in my car the other day and after replacing it, the engine refused to start. It turned over but would not run! To my knowledge the COMs was serviceable but the plip did not unlock the car either. I checked the functions of the COMs and all of the buttons and levers worked. At the time I was 'fiddling' around with BSI and engine ECU parameters in the LEXIA program. I thought for a while that I had wiped the key programing from the engine ECU. I soiled my armor as Monty Python might say!
I postulated that the problem might be with the COMs unit and so I reinstalled the original COMs unit. Sure enough the engine started and ran on cue.
So what's the take away here? Seeing as the central locking did not work but all of the "mechanical" functions of the COMs unit did work I started to suspect the RF receiver module. I believe the RF module in the top of the COMs unit manages both the central locking signal from the plip and polling of the RFID tag in the key. I initially thought that the module just handled the central locking but I now believe it handles the RFID chip in the key too.
cruise control 038.jpg
The RF module that sits in the top of the COMs unit.

Not ground breaking news but I hope I didn't bore too many people? ;-)
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