Code VCSEC_a021 was reported by the “Security and keys (VCSEC)” controller in the car. The letter “a” in the middle places it among entries of the alert type.
Vehicle Controller Security — vehicle security, the alarm, key fobs, phone-as-key over Bluetooth and pairing the tyre pressure sensors. These codes often appear after changing a key, a wheel or a battery.
The most common type. The car logged the event and may have shown it on the screen. The range is wide — from something trivial that clears itself to something that needs attention.
This is how the fault is named inside the car's firmware. For codes without a description it is the most precise clue there is — the name itself says what the event is about.
The text below comes from Tesla's technical documentation. We leave it in the original English so that translation cannot shift its meaning.
Drive with caution
AC charging interrupted
Acceleration reduced
Battery charge level too low
Schedule service
Active hood deployed
Pull over safely
Suspension may not be level
Ride comfort may be reduced
Air compressor faulted
PULL OVER SAFELY
Air compressor not started
Air conditioning reduced
Vehicle systems being cooled
Check air pressure in tires
Vehicle unable to raise
Unable to adjust height
Timeout elapsed
Ultrasonic sensors covered
Use brake pedal when stopping
Autopark aborted
Autopark canceled
Take control
Autopark enabled
Autopilot cameras unavailable
Autopilot computer rebooting
Autopilot features limited
Autopilot limited
Steering angle saturated
Steering rate saturated
Camera alignment required
Autopilot trial expired
Autosteer not enabled
Go to Autopilot settings
Autosteer unavailable
BCCEN internal error
Battery charge level low
Charge now
Battery charge level very low
Charge immediately
Battery is heating
Battery power very low
Heating and A/C reduced
Both pedals pressed
Motor power reduced
Motor power removed
Brake fluid low
Brake temperature high
Braking functions degraded
CAN bus fault
CHAdeMO charging issue
Center Display unavailable.
Maximum charge rate reduced
Charge port disabled
Charging unavailable
Charge port door sensor fault
Charge port latch not engaged
Charge port requires service
Charging may be unavailable
Charge rate reduced
Service is required
Disconnect cable and retry
Charging adapter fault
Unplug and retry
Charging will start soon
Charging equipment fault
Charging equipment not ready
Charging speed reduced
Charging stopped
Close console lid gently
Coolant pumps require service
PULL OVER IMMEDIATELY
Cruise Control canceled
Unable to maintain speed
Cruise control disabled
Cruise control speed reduced
Cruise control unavailable
Obstacle in path
Cruise control will not brake
Try AC charging
Use drive larger than 32GB
Reformat drive as exFAT
Reformat drive to restore
Door open
Proceed with caution
Drive not authorized
Key authentication required
Drive system shut down
Driver's door open
EBuck configuration set
DO NOT DRIVE
Electrical system power low
Vehicle shutting down
Emergency brake applied
Emergency brake not applied
Release Park button and retry
Entering Transport Mode
Press brake pedal to continue
Retry or manually move door
Falcon door open
Front defroster limited
Front left headlamp fault
Check light when convenient
Front motor disabled
Power reduced
Unable to detect occupants
Front right headlamp fault
Front trunk open
GPS antenna disconnected
Gateway SD card failure
Gear stalk malfunction
Headlights manually set to ON
High beam control malfunction
Hold N for Neutral
Move vehicle to flatter area
Display is off
Jack mode enabled
Suspension leveling disabled
Key fob battery low
See Owner's Manual to replace
Key not detected
Key not inside vehicle
Unable to drive
BCCEN provisioning required
Keyfob may not function
Provision BCCEN
Launch mode enabled
Left fascia light fault
Left turn signal fault
May require BCCEN replacement
Low Air Pressure
Clear files to make space
Manual door release used
Motor overheating
Release accelerator pedal
Out of data roaming area
Park Assist unavailable
Park button malfunction
Parking brake did not release
Retry shift out of Park
Parking brake in Service mode
Parking brake not applied
Vehicle may free roll
Parking brake not set
Vehicle may be free rolling
Press park button to reset
Schedule service immediately
Power Reduced
Power braking assist reduced
Power limited - OK to drive
Vehicle systems shutting down
Powertrain requires service
Press brake pedal to drive
Raising suspension
Based on location
To improve ride comfort
Rear Axle 2 Motor Overheating
Vehicle power may be limited
Rear left motor power reduced
Rear motor disabled
Rear seat belt unbuckled
Regenerative braking disabled
Deceleration reduced
Deceleration increased
Restart vehicle to drive
Right fascia light fault
Right turn signal fault
Safety restraint system fault
Second row seat unlatched
Selected level not allowed
Schedule service now
Shift into D or R to drive
Showroom Mode enabled
Drive not allowed
Immediate service is required
Side Collision Assist event
Slip Start enabled
Software update required
Unable to start vehicle
Update BCCEN
Stability control disabled
Steering assist reduced
Supercharger anomaly detected
Supercharger fault
Try a different stall
Supercharging not enabled
Take control immediately
Vehicle departing lane
Push seat base up then down
To maintain set speed
Place hands on steering wheel
To release Vehicle Hold
Touchscreen unresponsive
Traction control reduced
Trunk open
Unplug device from USB port
USB drive has no filesystem
Unable to AC charge
Unable to DC Fast Charge
Disconnect and retry
Unable to charge
Check charging equipment
Wall Connector needs service
Close charge port door
Immobilizer pairing required
Remove charge cable
Voltage supply too low
Unable to heat battery
Charge soon to improve power
Unable to precondition cabin
Door or trunk open
Unclear pedal press
Press brake to reset
Update reservation
connected key is expiring
Use key card
Vehicle coolant is low
Vehicle may not restart
Vehicle skidding
Vehicle speed limited
Vehicle systems too cold
Vehicle systems too hot
Vehicle systems very cold
Charge speed reduced
Vehicle trying to hibernate
Charge vehicle to recover
Vehicle unable to charge
Walk-Away lock unavailable
Weak power source
Unable to charge battery
Windshield washer fluid low
Windshield wipers disabled
Wiper button malfunction
Copy it exactly, letter and number included. Photographing the screen is safest — codes often differ by a single digit, and mixing them up leads somewhere else entirely.
Some codes clear after a screen restart or after the car sits locked for a few hours. If the code does not come back, it was usually a one-off glitch.
A one-off entry and a code that appears after every drive are two different things. It helps a service centre enormously if you know exactly when it shows up.
With airbags, brakes, steering and high voltage there is no point waiting it out. With the other groups you can watch and see whether the code returns at all.
Error codes are only part of the picture. For cars on TesList you also see battery health pulled straight from the vehicle, plus a price calculator that works out from current listings what a given car is actually worth today.