Checking The Function

Fig 1: Identifying Ignition ON

Courtesy of VOLVO CARS CORPORATION

Ignition on.
Gear selector in position P
Try moving the gear selector to another position without depressing the brake pedal. It should not be possible to move the gear selector.
Depress the brake pedal and try moving the gear selector to another position. It should now be possible to move the gear selector.
If the function is correct, this is an indication that the fault was present previously but is not active at the moment, i. e. an intermittent fault.