Citroen C5 Aircross Quiz
Immobiliser

Operating principle: immobiliser

In this manual: Immobiliser
AAS - Parking Aid — 8Owner's Manual Citroën C5 II — 139Citroen C5 Aircross (2017- 2024) - Owner's Manual — 143Audio system — 14Overspeed control — 7Multifunction display — 4Driver information instrument cluster — 20Navigation assistance — 8Intruder alarm — 7Mechanical specifications — 9Power supply — 8Electrical equipment — 13Lighting and electrical equipment — 3Immobiliser — 4Sunroof — 10Exterior lighting / signalling — 38Multiplexing — 7Air conditioning — 7Body — 6General specifications — 9Automatic gearbox control — 3Exterior mirrors — 10Airbags — 5Defrost — 6Underinflation — 6Interior lighting — 4Wipers / Washers — 6Window lifters — 11Cooling — 8Opening management — 7Cruise control — 5Suspension — 4Grip management — 1Paint — 2Exterior lighting control — 1Indicators (turn signals) — 1Automatic lighting systems - General recommendations — 1Wiper control — 1Special position of the front wipers — 1
~2min read

To unlock the engine control unit:

  • the ignition key with transponder must be identified,
  • and the ignition key with transponder must be authenticated,
  • and the engine control unit and the BSI must be paired.

START OF UNLOCKING SEQUENCE

When a door is opened, the BSI sends an identification request to the ignition key transponder:

  • for 2 minutes while no response is received,
  • or when +ACC appears, if no response is received before the end of the 2 minutes.

KEY IDENTIFICATION

Identification de la cle
Key identification

AUTHENTIFICATION DE LA CLE

KEY AUTHENTICATION

Authentification de la cle

Note: The encryption key is uniquely determined from the BSI code. It is known by the BSI and the transponder tag.

ENGINE CONTROL UNIT UNLOCKING

STEPS

DESCRIPTIONS
1 When +APC appears, the engine control unit sends a random number to the BSI.
2 The BSI calculates a link authentication number from the random number, the BSI code and a secret function.
3 At the same time, the engine control unit performs the same calculation.
4 If the key has been authenticated, the BSI sends the link authentication number it calculated to the engine control unit.
5 The engine control unit compares the link authentication number received from the BSI with the one it calculated.
6 If the numbers are identical, the engine control unit unlocks.
If the numbers are different, the engine control unit remains locked.

Important: After 3 unsuccessful unlocking procedures, the starting sequence is disabled for 1 minute.

ENGINE CONTROL UNIT LOCKING

After +APC disappears, a 10-second time delay starts. At the end of the delay, the engine control unit locks. Engine starting is then impossible. When the engine control unit is no longer powered, it locks automatically.

IMMOBILISER STATUS DISPLAY

Visualisation de l'etat de l'antidemarrage

Test yourself

A quick Citroen C5 Aircross quiz: every answer comes with an explanation and a link to the manual page.