viper 5901 siren not working

I just finished wiring up a viper 5901 to my car and everything seems to work fine except for the siren. The doors locks/unlocks and the parking lights flash normally however, I do not get a siren confirmation chirp. Triggering the alarm does not make the siren off either and I know for sure that the alarm isn't in valet mode. There shouldn't be anything wrong with the siren because it sounds fine if I connect the red lead to battery positive. Disconnecting the ground wire for the alarm makes the siren sound but at very low level when I lock/unlock the car. I also used a dmm to measure the voltage output from the brain's brown siren output wire and was only getting something like 4v; shouldn't it be 12v? Would this indicate that there is something wrong with the siren output part of the alarm?

update: the output on the siren wire when alarm is triggered is actually only ~0.85v

check to make sure that you didn't turn off the confirmation chirps by mistake.Protect what's yours.

No the OP mentioned no sound when triggering and he's right it should be 12V+ on trigger or chirp.

i gave up on trying to use the siren output wire and instead, wired the siren to the horn output wire using a relay. still get the confirmation, and warning chirps however, the full trigger alert no longer sounds the same as if it was hooked up to the siren output wire.

If you are able, disassemble the alarm brain, follow the trace from the siren connection pin, it should go to a transistor.  Can you read the number from the transistor?  Do you have or have access to a digital multimeter?