DRV8434S: Cannot trigger OL fault

Part Number: DRV8434S

Tool/software:

I have had good success using the Stepper Driver. However, when trying to detect a disconnected motor, I am unable to latch the OL bit in the FAULT register. All control is via SPI. The programming is on an Arduino platform (M0+ controller) with a Pololu software driver. The software driver and the Motor Driver have worked very well up to this point, with successful speed, direction, and DAC control. 

Vref is 0.670 V

TRQ_DAC is 75%. 

CTRL4 is 0x08. I tried 0xB8

Microstep_Mode 0x01

A tight loop test routine executes 20 steps with 2 ms between steps in the hope of triggering a OL.

FAULT register returns 0x00 after the 20 steps.

Suggestions appreciated.