Sim800l problem.

For first sorry for my bad English.
I have problem with Sim800l module. I power it using DC-DC converter on LM2596. When I send AT+ commands it says error. If it isn't, module restarts.

Say i running AT+SABPR=3,1,"apn","PROVIDER_APN" if result is OK, then after OK it prints

Call ready.
Sms ready.

etc., witch means that module was restarted. Also it prints empty lines that are seen if i decrease com monitor size.

Anybody can help me to solve problem?

Tryed to connect rst to VCC3.3. No result. DC-DC output voltage is 4V. Input voltage for whole project is 9V. DC-DC input is parallel connected with Arduino's input jack. Arduino board is Arduino Uno R3 with chip ATMEGA328P

Which SIM800L module? Link?

This

Are you using a level shifter on the Rx/Tx lines?

http://forum.arduino.cc/index.php?topic=496064.0

Only resistors 1kOhm