Changed the bcm and now wont start - 2002 Chevrolet TrailBlazer

Your best bet , have a qualified repair shop check it out . The windshield wipers / washer are controlled by the BCM - body control module .

Wiper/Washer System Description
The body control module (BCM) controls wiper motor low speed operation. The washer pump and high speed operation are controlled directly by the wiper/washer switch. The windshield wiper/washer switch supplies voltage on the signal circuits to the BCM for windshield wiper/washer operation. When WASH, MIST, DELAY, LOW, or HIGH is detected, the BCM energizes the wiper micro relay by suppling voltage to the relay coil. This allows battery voltage from the WIPER fuse to flow through the relay switched input then through the contacts and out the relay switched output to the wiper 2 relay switch contacts. Since the wiper 2 relay switch contacts are normally closed to the low speed circuit of the windshield wiper motor, the motor will operate at low speed.
The BCM is the gateway to all the modules on the vehicle , all are connected to a serial data network for sharing info.
Having a factory or some other type of a professional scan tool that can view BCM DTC'S - diagnostic trouble code's would be the first thing in the diagnostic procedure . If the BCM or wiper switch is causing a problem - shorted etc... it wont allow the BCM to message other modules , like the anti-theft system or engine computer , so the PCM/ECM - engine computer wont see message for the request for start . You need to know how the start system works also.
Circuit Description
Moving the ignition switch to the START position signals the body control module (BCM) that engine crank has been requested. The BCM verifies that theft is not active and sends a serial data message to the powertrain control module (PCM) requesting engine start. The BCM also energizes the RUN/CRANK RELAY. When the RUN/CRANK RELAY switch side closes, and the vehicle is in Park/Neutral or with the clutch fully depressed, if equipped, supply voltage is applied to the PCM CNTRL relay coil. The PCM verifies the transmission is in Park/Neutral or if the clutch is fully depressed, if equipped. The PCM will then ground the control circuit of the PCM CNTRL relay, closing the switch suppling voltage to the starter solenoid. On some vehicles the starter will continue to crank the engine with the key released until it starts, the crank command has timed out to prevent excessive heat build up in the starter circuitry or the PCM receives an engine run flag.
There is nothing your going to be able to do , nor should you try . So do yourself a favor an take it to a qualified repair shop.

What make , model an year vehicle ? Changed BCM - was it programmed to your vehicle ? Dealer

Sounds like an ignition switch,,,,could be a main fuse problem

When you changed the BCM you basically disabled the car, the Key will have to be reprogrammed to the cars immobilizer, that is if the immobilizer is still good, If the BCM shorted (Burnt) out, it could have affected other components in the car. I would let the dealer run a diagnostic on the car. They may be able to reflash the ECM / BCM and immobilizer or they may have to replace them.

The shifter release solenoid is activated by the brake light switch. Check to see if the brake lights are working when you press the brake pedal. If not, that may be the reason why the shifter won't come out of park. You may need to replace or adjust the brake light switch. (It's located at the top of the brake pedal arm).

Did you get the part new or salvaged, if salvaged make sure the numbers and letters are the same on the part you swapped

YOU NEED TO TAKE IT TO A CERTIFIED STATION AND HAVE IT PROGRAMMED FOR THE NEW BCM !!!!!!!
IT IS REQUIRED
IF IT STARTS WITH OLD ONE PUT IT BACK IN AND DRIVE IT TO REPAIR FACILITY THEN CHANGE IT OUT AGAIN AND HAVE THEM PUSH IT IN AND REPROGRAM IT FOR YOU !!!!!!!

Any PCM, BCM, or ignition switch assembly that's replaced requires what's described as a Passlock re-learn procedure to synchronize the three subassemblies for proper operation. This either takes place at Saturn or during a 30-minute DIY procedure in three 10-minute cycles. The procedure is basically to leave the ignition ON for 10-minutes, cycling the ignition OFF and then ON for another 10-minutes and once more until repeated three times, never starting at any time. After the third cycle the ignition can be turned to start the engine to confirm that all components have successfully been synchronized. A failure to start means an incorrect re-learn procedure was done and needs to be repeated all over again. The security light will flash during the process and eventually turn off altogether as indication of successful re-learing security codes for any new part replaced. What isn't changed are the VIN and mileage that Saturn equipment can do. The security system is divided into three parts; the ignition switch sensors, the PCM, and the BCM. Any one of these subassemblies being replaced requires the BCM to relearn the new replacement part otherwise you'll just have a dead engine unable to run. New BCM's come as blanks that Saturn address' with their Techtool II with VIN and mileage copied from the failed BCM. 'Field' BCM's removed from vehicles still retain VIN and mileage that can only be changed by Saturn. There may be other programmed accessories that have to considered to be compatible to the original one removed for replacement.

key remotes

Replacing the BCM will require the remotes to be reprogammed. The problem is that you need a scan tool with the proper software to perform the programming. Here is the procedure for reprogramming if you have access to a tool. If not you should put a call into a local garage that does diagnostic work or the dealer. If it were just a battery change you could resync without programming.

Is the security light flashing on the dash... If so , the enabler in your key is worn. This means the ingnition tumbler needs to be changed. E-mail me more details

Well your not going to like this but I think I can help im assuming you checked all the fuses inside the car and under the hood ? if there all good your problem more than likley is in the BCM as it controls the lights and blikers BCM stands for Body Control Module. good luck :)