A mobile communication system of a motor vehicle includes a primary antenna. The system further includes a telematics module having a processor and at least one memory including a computer program code. The memory and the computer program code are configured to, with the processor, cause the system to detect a predetermined vehicle event and measure a primary signal quality of the reference signal received at the primary antenna. The memory and the computer program code are configured to, with the processor, cause the system to determine a maximum primary signal quality and compare the maximum primary signal quality with a threshold. The memory and the computer program code are configured to, with the processor, cause the system to determine a defect in the primary antenna and activate a diagnostic trouble code associated with the defect, in response to determining that the primary maximum signal quality is below the threshold.