The Key and Waking the Car Up
Before anything else can happen, the car has to notice you, wake up, and decide that the key in your hand is allowed to start this particular vehicle.
In plain language
A parked MINI is not switched off in the way a lamp is switched off. A small number of circuits stay awake — the alarm, the receiver listening for the remote, the locking system and the memory that holds the car's settings — while the rest of the car is powered down to protect the battery.
Opening the door, pressing the remote or, on cars with comfort access, simply carrying the key close enough, wakes that system. It then performs a security check: is this key known to this car, and is it authorised to start it? Only when the answer is yes will the car allow the next step. This is also why a car with a flat or weak battery can behave strangely before it ever gets as far as cranking.
What the customer sees
Locks that respond slowly or not at all; a key that works at the door but not for starting; a car that needs the key held against the start button; interior lights or a display that come up and then drop out again.
What the module is doing
Listening while asleep on the small number of circuits that remain powered, then waking the access and body systems and the communication networks when an event arrives. The access system exchanges a security dialogue with the key, decides whether it is authorised, and publishes that result to the modules that need it.
What a technician tests
Battery and supply first, because almost every odd wake-up symptom is really an electrical one. Then whether the wake-up event is reaching the access system, whether the key is being recognised, whether authorisation is being granted, and whether that result is reaching the engine-management side of the car.
The technical detail
Sleep is a managed state, not an absence of power. Selected security, locking, alarm, receiver and memory circuits are supplied continuously. Everything else is shut down under the control of the vehicle's power-management strategy, which is also watching battery condition and will progressively restrict functions as that condition falls.
Wake-up is an event. A door handle, a lock request, a remote button, a comfort-access detection or a start-button press produces a signal that brings the access/body system out of sleep. That system in turn wakes the networks, and the other modules on those networks come up in turn.
Authorisation is separate from unlocking. Being able to open the doors does not mean the key is authorised to start the engine. Across MINI generations the immobiliser and access functions have been carried by different modules with different names, and the way the key is detected has moved from a physical switch and slot to proximity detection. What has not changed is the principle: the engine-management module will not deliver fuel and spark until the security system tells it the key is authorised.
Power modes describe how awake the car is. Terminal designations describe which supply groups are switched on for a given mode, and modern MINIs manage those groups actively — deactivating some of them to protect the battery, or refusing to enter a higher mode when battery condition is poor. A power mode that will not advance is a legitimate diagnostic finding, not a glitch.
Why this matters when something goes wrong
A key or authorisation complaint is diagnosed by finding where the chain stops: no wake-up, no recognition, recognition but no authorisation, or authorisation that never reaches the engine-management module. Those four are different faults with different causes, and only the first is a "nothing happens at all" complaint.
Because the access system also owns terminal and power-management functions, its fault memory often records battery and terminal events. A car that has been standing, jump-started or run down will generate exactly that kind of record, which is why these codes are read alongside battery condition rather than in isolation.