Systems and methods for external access detection and recovery in a subsystem of a system-on-a-chip (SoC) in a portable computing device (PCD) are presented. In operation, a subsystem of the SoC is operated in an internal mode independently of the SoC while the SoC is in a low power state, such as a non-functional or zero power state or mode. The subsystem comprises a processor in communication with a memory, a sensor, and a monitor module. The monitor module detects when the processor of the subsystem requests access to a component external to the subsystem. In response to this detected request, the SoC is caused to enter into a full power state or mode, and the subsystem is caused to exit the internal mode of operation.