DRV8243-Q1: SDO line issue

I have interface the motor driver DRV8243PQDGQRQ1 with my MCU. When i probe my DSO with  SPI lines (SCLK,SDO,SDI), motor runs. If i remove the probe, SPI communication fails.

But even i touch the SDO line with open probe, motor runs. What could be the possible reasons?

MCU supply = 5V

Driver VDD=5V ,Vm=12V ,

We use SPI -P variant.

Ipropi and Itrip not using.