The alarm is going off at random - at night only! It had the siren replaced a month ago because it kept giving out the 4 beeps when the keys were removed from the ignition. I ripped apart the old siren and found the problem was caused by corrosion - a cheap cure if you can split the unit without destroying it. Anyway, the hazard led shows no errors. Does the tech2 unit show why alarms went off, or only errors in the system? My dealer says it maybe the rear window sensors - replacement will be very expensive. Any ideas? TIA, Mike.