When I connect via Serial, Roboteq goes into test mode

I connected to Roboteq via USB-to-Serial and sent commands from PC. It was working. Then I connected Roboteq to Arduino via TTL-Serial adapter. The adapter got power from Roboteq. However, when I turned power on, Roboteq went into test mode (full speed, reverse speed, etc).

I checked that Arduino worked and sent commands to Serial port - I connected PC to TTL-Serial adapter and saw them. Let me remind you that the power was taken from Roboteq.

When I power the adapter and Arduino, wait 1 sec and then turn on Roboteq - everything works fine.

How do I solve this problem?

FID=Roboteq v1.3 RCB400 03/11/2014

Download and install the latest firmware from our web site. The selftest function has been removed.