A diagnostic apparatus for diagnosing a fault within a lighting system, the lighting system comprising a luminaire and a presence sensor (123, 151), wherein the presence sensor is configured to control a light output characteristic of the luminaire based on detecting an object within a sensing range, the diagnostic apparatus comprising: an interface configured to receive, from a user, an input to control the luminaire, wherein the received input is indicative of the user being within the sensing range of the presence sensor, a fault determiner configured to determine a lighting system status and a lighting system fault, wherein the lighting system fault is based on the received input and the determined lighting system status, and a fault reporter configured to generate a fault report based on the determined lighting system fault; characterized in that the diagnostic apparatus further comprises: a sensor determiner configured to determine a status of the presence sensor (123, 151), wherein the fault determiner is configured to determine the lighting system status based on receiving the status of the presence sensor, and further configured to determine a type of lighting system fault based on the lighting system status and the received input; and wherein the fault determiner is configured to determine a presence sensor fault when the sensor determiner fails to produce an output indicating the presence sensor detecting an object indicative of the user being within the sensing range. an interface configured to receive, from a user, an input to control the luminaire, wherein the received input is indicative of the user being within the sensing range of the presence sensor, a fault determiner configured to determine a lighting system status and a lighting system fault, wherein the lighting system fault is based on the received input and the determined lighting system status, and a fault reporter configured to generate a fault report based on the determined lighting system fault; characterized in that the diagnostic apparatus further comprises: a sensor determiner configured to determine a status of the presence sensor (123, 151), wherein the fault determiner is configured to determine the lighting system status based on receiving the status of the presence sensor, and further configured to determine a type of lighting system fault based on the lighting system status and the received input; and wherein the fault determiner is configured to determine a presence sensor fault when the sensor determiner fails to produce an output indicating the presence sensor detecting an object indicative of the user being within the sensing range. a sensor determiner configured to determine a status of the presence sensor (123, 151), wherein the fault determiner is configured to determine the lighting system status based on receiving the status of the presence sensor, and further configured to determine a type of lighting system fault based on the lighting system status and the received input; and wherein the fault determiner is configured to determine a presence sensor fault when the sensor determiner fails to produce an output indicating the presence sensor detecting an object indicative of the user being within the sensing range.