1. Checking the indicator.
A) Disconnect the connector from the sensor and then ground the connector on the wire side.
b) Turn on "ignition": The indicator should be on. If the indicator does not light up, then check the indicator lamp.
2. Checking the sensor-switch.
A) Check for continuity between the terminal and sensor nut when the parking brake is applied.
b) Check for continuity between the sensor terminal and nut when the parking brake is released.