You have several options you can disassemble the entrance bush and remove the bulb

<-(I don't entertain it is joke hehe).
Or go to the engine and on the gearbox there are some tubes and a temperature sensor change it and it is already. or if this is not in the bottle of Espansion Abeces there is. removing the cable the light will turn off and connecting that cable to the vehicle's chassis the light will turn on, so you know that it is the one who fails.