viper 770 strange issue

Vehicle is a 2007 Toyota FJ Cruiser, and unit is as posted in subject line, Viper 770 Remote Start/Alarm Combo. Problem is, when the alarm is triggered, the brain fries. What I mean to say is, when the siren goes off, all it will do is continuously chirp at low volume, and after this point the unit is dead. It will not link to a BitWriter, nor will it go into a Valet or serviceable state of any kind. Have tried two brains, same results. Wiring appears accurate and the unit functions 100% until the alarm is triggered. Thoughts?

I'd suggest testing every wire at the alarm plug and make sure they are all metering properly.  It sounds like something isn't hooked up right.

I agree with Steven. I know that on many alarms, when the ground isn't connected, the siren will sound very quietly as you describe. On all the plugs that enter the alarm's brain, there's just a little bit of metal contact exposed. Make sure you're putting your test light/meter's probe directly on that metal part. This way, all in one shot, you're testing all possible failure points.

On this particular unit, do you believe it may be caused by the fact that my siren ground is connected to the same ground as the one in the vehicle? During prep, I ran the ground and Siren +12V Output from the main harness, instead of grounding the siren separately. I usually do this without problems, but then again I don't do a ton of DEI. Thanks for your quick replies guys, I'll meter the unit this morning before I install a different unit.

Check your brown siren output wire, it seems to be getting grounded out somewhere down the line.

dmielken wrote: On this particular unit, do you believe it may be caused by the fact that my siren ground is connected to the same ground as the one in the vehicle? During prep, I ran the ground and Siren +12V Output from the main harness, instead of grounding the siren separately. I usually do this without problems, but then again I don't do a ton of DEI. Thanks for your quick replies guys, I'll meter the unit this morning before I install a different unit.

That's how I do all my alarms and never have a problem.