Having done it many times now I thought i'd document the process.
Many cars no longer have working Plips or never had one installed in the first place, so you may wish to install your own with the added benefit of not having to point your fob through the window!
The installation costs less than a tenner and takes half an hour for the more adept hands or an hour for the novice.
To carry out the job you will require:
10mm socket wrench
Wire snips
Electrical tape
Soldering iron (optional)
One of these (or similar) http://www.ebay.co.uk/itm/280935117931" onclick="window.open(this.href);return false;
The process:
Your central locking controller is located under here:
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After sliding the left front seat right forward just pop the oddment pocket out of the back of the console (pictured) & remove the 10mm nut & washer, then at the front of it remove the round plastic cap & remove the 10mm bolt. With the handbrake in the UP position just lift the console up from the back and fold forward until it removes completely. (some higher spec models have a 12v accessory socket in the back of the console, this will need to be unplugged).
This will reveal this:
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Unplug the module so you can't damage it (it has a constant live connection)
The plug is numbered thus:
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Now you will need to look at your Chinenglish instruction manual that came with your kit. You are normally presented with 3 options. Negative Trigger, Positive Trigger, Positive AND Negative Trigger. For the BX you will require the NEGATIVE TRIGGER diagram.
Something like this:
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The installation requires only 4 wires: Live, Negative, Lock Trigger and Unlock Trigger. (on some kits you may have to bridge a pair of wires for the triggers making 6 wires but they still only connect to 4 on the car). Trim the loom that came with your kit leaving 6-8 inches of wires as there's little space for excess. Most of these kits can also trigger your lights to flash too but I've found that pointless and the original Plip didn't!
Once you have identified the wires required connect them to the wires on the above plug in the following order (I splice & solder but you can use whatever method you prefer but not scotchblocks, they're crap):
Lock Trigger to either wire at number 7
Unlock Trigger to either wire at number 5
Negative at number 2
Positive (live) at number 1 - Ensure this one is very well insulated.
Gather & tape up the remaining spare wires.
It should then look something like this:
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Refit the original control module & test. You should now have Remote Central Locking! Well Done!
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Refit the centre console with the original module back in the correct place, the new module will fit snuggly down the opposite side of the handbrake. Ensure you route the cable neatly and well away from the handbrake levers mechanism, then refit the oddment tray.
Tidy up, put a plaster on that cut, make tea & feel smug.