I have a L reg Vauxhall astra saloon. I do not have a key fob for activating the alarm just my door key. after locking the car and walking away the alarm self activates, i have to return to the car and unlock and re-lock the car to turn it off. i have disconnected the sounding horn so as not to annoy the neighbours (n/s/f wing) today turning the key did not dissable the alarm or immobiliser, i had to hunt around the car to find out where the alarm was (o/s footwell) and started pulling apart sockets - to no avail then all of a sudden while plugging it all back in again - it dissarmed. every now and then my ECU light flashes on then off. What the hell is going on and how can i fix it.? Vauxhall dealers are no help at all!!

Gary Scott, June 2007

Hi,
It seems you now have two problems; first is the alarm, and next the ECU light flashing after you disconnected those plugs. The best way to sort your alarm is to try and identify the manufacturer, it's not always a generic "vauxhall" system. Once you have the make and if possible, the model of alarm, you can search the net. The makers of alarms are really good at supplying diagrams, info, etc, unlike the car makers themselves. The ECU is a different issue, the best source of info is the vauxhall owners web site, where the knowledge of specific vauxhall snags is very good. It sounds like you might have pulled and reconnected a plug that feeds information to the ECU, and apart from disconnecting your battery for 20 minutes or so to "reset" the ECU, I'm not sure what to advise.
Cheers now

Ken Chapman, June 2007