This device is used to create a dynamic ambient inside the car. It connects to the ECU and retrieves the RPM and set the interior light according to the reading.

STEP 0: Enter the AT mode
STEP 1: Reset the module to factory settings: AT+ORGL
STEP 2: Set master mode: AT+ROLE=1
STEP 3: Set inquire parameters: AT+INQM=1,9,48
STEP 4: Search for device: AT+INQ; Note the MAC address of your ELM327
STEP 5: Set HC-05 to connect only to the ELM327: AT_CMODE=0
STEP 6: Bind to the address: AT+BIND=1234,56,ABCDEF; Replace with the MAC address from STEP 4
STEP 7: Pair to the address: AT+PAIR=1234,56,ABCDEF,20; Replace with the MAC address from STEP 4; Last parameter is the timeout
STEP 8: Pair to the address: AT+LINK=1234,56,ABCDEF; Replace with the MAC address from STEP 4

Demo
Complete presentation
HC-05 AT commands