A troubleshooting method for debugging wireless sensor nodes using measurements of the supply current waveform and logic outputs is presented. The troubleshooting and debugging technique uses the supply current waveform in conjunction with the measurement of one or more logic output signals to assess problems which cannot be resolved using only the standard debugging interface for the node’s microcontroller like the JTAG debugger. The usage of logic output has a minimal probing effect on the sensor node’s firmware adding a minimum of 2 instructions in the simplest case. These measurements have been successfully used to monitor and troubleshoot a custom developed ultra low power sensor node (Fig. 3b).