"Secure" on a red background indicates that there is a problem in the link between Navigation control unit and Audio, suggesting that there is either a Navigation system fault or the Navigation control unit has previously been fitted in another vehicle.
"Secure" on a green background indicates that there is a problem in the link between NATS IMMU and Audio, suggesting that there is an audio fault or the audio unit has previously been fitted in another vehicle.
"Secure" on a yellow background indicates that the transponder (NATS key) is not working correctly or it has previously been fitted in another vehicle.
When a "Secure" message (of any type) is displayed, it can be cleared by re-initialising the NATS system using CONSULT-II and the immobiliser PIN code (there is no need to return the audio to a Clarion service centre). If re-initialising fails to clear a "Secure" message then the component or its circuit (identified by background colour) may be faulty and should be inspected.
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So it's a anti-theft feature that locks operation if the Navi control unit has been has previously been fitted in another vehicle.
Drive to your Nissan dealer and ask if they can fix this issue.
A.R.S., October 2012