The IR 2016 contains a small lithium battery on the main board. When it dies, system settings can become scrambled, leading to false error states.

If the hardware connections are secure but the error persists, the firmware may be corrupted. This requires a service tool (SST or Service Support Tool) and a USB connection to a PC.

file, a failed update, or a communication failure between internal components. JustAnswer Incident Report: Canon iR 2016 "Download Standby" Error Error Status Primary Cause Corrupted or missing firmware/system software. Secondary Causes