I have a 2005 Chevrolet Trailblazer LT. The "service brake system" came on and the vehicle won't start.

Chevrolet TrailBlazer - Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Chevrolet_TrailBlazer
WikipediaProduction of the Blazer overlapped with the TrailBlazer until 2005, when the 2-door ...2006-2008 Chevrolet TrailBlazer LT ... The Active Fuel Management system on the V8 engine shuts off 4 of the 8 ... 2003-2005 Chevrolet TrailBlazer EXT.

Trailblazer cranks but won't start - first things to check ...

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www.youtube.com/watch?v=4O-wplilVV0

Mar 6, 2012 - Uploaded by MAY03LT
These are the first tests that I do when I have a Trailblazer that won't start. ... Car will not start trouble shooting guide, wontcrank, wont turn over, etc. ... Chevy Trailblazer - testing fuel pressure 2002 -2004 4.2 I6 - Duration: 4:34.

Service Stability System Message The message center displays the service stability system message when any one of many VSES-disabling DTCs is set. The EBCM sends a serial data message to the IPC requesting this display.
It means there is a problem an till you get it fixed the stability control system is disabled ! ( EBCM ) electronic brake control module Has detected a problem an set a DTC - diagnostic trouble code in it's memory an had the message displayed !
Vehicle Stability Enhancement System (VSES)
The vehicle stability enhancement system (VSES) provides added stability during aggressive maneuvers. Yaw rate is the rate of rotation about the vehicle's vertical axis. The VSES is activated when the electronic brake control module (EBCM) determines that the desired yaw rate does not match the actual yaw rate as measured by the yaw rate sensor.
The desired yaw rate is calculated by the EBCM using, primarily, the following inputs.
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The position of the steering wheel

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The speed of the vehicle

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The lateral, or sideways acceleration of the vehicle

The difference between the desired yaw rate and the actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. When a yaw rate error is detected, the EBCM attempts to correct the vehicle's yaw motion by applying brake pressure to one or more of the wheels. The amount of brake pressure which is applied varies, depending on the correction required. The engine torque may be reduced also, if it is necessary to slow the vehicle while maintaining stability.
VSES activations generally occur in turns during aggressive driving. When braking during VSES activation, the pedal may pulsate. The brake pedal pulsates at a higher frequency during VSES activation than during ABS activation.


It

ALL brakes locked up, or just rear? Rear could mean differential is locked up...Sounds more likely while driving it, as cars now have a front or rear valve so all brakes are not lost at one time..

check cruise control fuse and check the brake lights see if brake light working because the brake light switch will deactivate cruise control when brakes is applied.if brake lights dont work either fuse blowed or switch bad.if all is good have vechicle code scan because cruise control control by PCM and vechicle speed sensor and thottle actuator control motor.

Could be the brake switch or the solenoid that locks the shifter in park.
That circuit would need to be tested.

Can you disconnect the cable from the trans to see if the problem is in the shifter or in the transmission ?

Try shifter cable

This might be due to a failing antitheft system. Very common on GM vehicles. This link explains. http://vatspasslockpasskeysecurityhelp.yolasite.com/

Check the mega fuse in the underhood fuse panel, picture below

won't turn on? you mean start?
do headlights come on?
check brake light won't keep it from starting