I can think of two things you should probably check. The first is the flasher relay, sorry I'm not sure where it is located for your vehicle (the security system probably sends its own brief 'pulse' to activate the lamps during security system arming, while the turn signals and emergency flashers require a flasher relay for prolonged on-off regulation of the lamps). The other might be a faulty dash wire (The security system signal probably gets sent directly through an electronic module, bypassing the manual circuitry of the interior turn signal lever and emergency switch). There are several manuals published for the Sienna that have the fuse/relay locations and wiring diagrams.
How can you manually release the emergency brake on the 1998 Toyota Sienna?
Check fuse or turn signal flasher
Sienna Miller's birth name is Sienna Rose Miller.
Sienna Guillory's birth name is Sienna Tiggy Guillory.
Sienna Joseph's birth name is Sienna Isabelle Joseph-Willie.
Sienna = シエナ
disconnect + on battery; when reconnected, you must reset alarm via trip switch (refer to your owner's manual regarding exactly how to reset -- for example, hold in button for xx seconds until alarm stops then release)
Maya Sienna Turner goes by Maya Sienna, and Maya Papaya.
Sienna is located in the country Egypt.
Anthony of Sienna died in 1585.
Sienna Cammeniti was created in 2008.
Sienna Day is 165 cm.
Sienna Aldridge is 5' 10".
Sienna Beckman is 5' 3".
Nicole Sienna is 5' 6".
Sienna Grace is 5' 7".
Sienna Gray is 5' 4".
Sienna Guillory is 5' 6".
Pedro Sienna was born in 1893.
Pedro Sienna died in 1972.
Sienna Morris was born in 1983.
Laurentian Pencil Crayon Sienna is No. 49, but Sienna Brown is 26.
Sienna Miller was born on December 28, 1981
Sienna Milano goes by MySiennaMilano.