Procedure for transmitting diagnostic data of a field device (FG1, FG2) in a process automation system, wherein the field device (FG1, FG2) is in communication with a higher-level unit via a communication loop (KS1, KS2), wherein the communication loop (KS1, KS2) has a power supply/measuring current with a direct current component, and wherein a communication module (KM1, KM2) is connected to the communication loop (KS1, KS2) in such a way that the communication module (KM1, KM2) is switched in parallel with the field device (FG1, FG2), wherein said procedure comprises the following steps: - Generation of communication pulses by means of the higher-level unit, wherein said communication pulses are modulated onto the direct current component of the communication loop (KS1, KS2) as alternating current or as alternating voltage, wherein the communication pulses are HART commands, wherein said commands contain an invalid command for the field device (FG1, FG2) or a reception address that is different to the network address of the field device (FG1, FG2); - Continuous storage of electrical energy in an energy storage unit of the communication module by means of a converter unit connected upstream from the energy storage unit up to a predefined limit value, wherein the converter unit converts the communication pulses into electrical energy; - Interrogation of the diagnostic data of the field device (FG1, FG2) by a communication command by means of an interrogation unit of the communication module (KM1, KM2); - Receipt of the diagnostic data of the field device (FG1, FG2) by the communication module (KM1, KM2) by means of a communication command sent by the field device and wireless transmission of the interrogated diagnostic data to a receiver unit by means of a transmission unit of the communication module (KM1, KM2) as soon as the electrical energy accumulated in the energy storage unit reaches or has exceeded the predefined limit value and/or if the communication module (KM1, KM2) receives a command to interrogate or transmit data. - Generation of communication pulses by means of the higher-level unit, wherein said communication pulses are modulated onto the direct current component of the communication loop (KS1, KS2) as alternating current or as alternating voltage, wherein the communication pulses are HART commands, wherein said commands contain an invalid command for the field device (FG1, FG2) or a reception address that is different to the network address of the field device (FG1, FG2); - Continuous storage of electrical energy in an energy storage unit of the communication module by means of a converter unit connected upstream from the energy storage unit up to a predefined limit value, wherein the converter unit converts the communication pulses into electrical energy; - Interrogation of the diagnostic data of the field device (FG1, FG2) by a communication command by means of an interrogation unit of the communication module (KM1, KM2); - Receipt of the diagnostic data of the field device (FG1, FG2) by the communication module (KM1, KM2) by means of a communication command sent by the field device and wireless transmission of the interrogated diagnostic data to a receiver unit by means of a transmission unit of the communication module (KM1, KM2) as soon as the electrical energy accumulated in the energy storage unit reaches or has exceeded the predefined limit value and/or if the communication module (KM1, KM2) receives a command to interrogate or transmit data.