a) Disconnect the fuel filter switch connector. Ground the connector terminal.
b) turn on the ignition: the indicator lamp should light.
If not, remove and check the lamp.
2. Checking the operation of the water presence sensor switch in the filter.
The original can be found on this resource (toyotaman)
a) check for conductivity between the switch terminals when the float is lowered.
b) check for conductivity between the switch terminals when the float is raised.
