After removing the lamp, inspect it. If the filament is burned out or the glass bulb is loose on the base, replace the lamp.
Accurate lamp test: connect the lamp through the wires to the battery. In this case, the polarity is not important. If the lamp does not light up, replace the lamp. Check for corrosion on the wire contacts and on the pump cartridge. Clean up contacts.
The probe lead must be connected to a reliable ground (bare metal) or to the negative battery terminal. test needle (+) hold on the current-carrying contact of the connector or pierce the current-carrying wire with it. If at this time the probe lights up and the lamp does not light, then there is an open in the lamp ground wire. To check this, connect a ground with an auxiliary wire to the lamp socket. The lamp should light up.
Lamps that have only current-carrying wiring are connected to the vehicle ground directly through their housing.
In the absence of voltage in the current-carrying wire of the pump (probe does not light up) possible switch failure. Check switch.