Code
P1612
CITROEN
P — Powertrain
Engine immobiliser function
Views:
UK: 4
EN: 5
RU: 5
AI status
Completed
Completed
100%
Causes
- Key transponder not recognized or damaged
- Faulty immobiliser antenna/coil around ignition barrel
- Wiring fault (power, ground or CAN) between BCM/SAM and engine ECU
- Blown fuse or low supply voltage to immobiliser/BCM
- Module software mismatch, corrupted immobiliser data or ECU swap
- Faulty BCM/SAM or engine ECU immobiliser circuitry
Symptoms
- Engine cranks but will not start or no-crank/no-start condition
- Security/immobiliser warning lamp illuminated or flashing on dash
- Vehicle may start intermittently or only with a specific key
- Remote locking/unlocking may be affected
- No starter enable signal from ECU
What to check
- Read and record all fault codes from engine ECU and BCM/SAM; check freeze frame data
- Try starting with a known-good spare key; observe changes
- Check dashboard immobiliser/security lamp behaviour during key turn
- Verify battery voltage and main fuses for BCM/immobiliser
- Inspect wiring and connectors at ignition barrel/antenna coil and at BCM/engine ECU
- Scan CAN bus for communication errors between modules
Signal parameters
- Key transponder ID / Key recognized flag (from BCM/immobiliser)
- Immobiliser status flag (enabled/disabled) in engine ECU
- Starter enable/immobiliser inhibit signal (digital)
- CAN messages between BCM/SAM and engine ECU (error counters, timeouts)
- Antenna coil continuity/resistance (Ω) and induced signal when key inserted
- Supply voltage to immobiliser module and associated grounds (V)
Diagnostic algorithm
- Connect a full-function diagnostic tool to read stored codes from engine ECU and BCM; note module-specific immobiliser faults.
- Attempt restart with original key and with spare key; note any differences and whether the security lamp extinguishes.
- Check battery voltage and main fuses/relays related to BCM and engine ECU; restore any poor power/ground connections.
- Inspect antenna/coil around ignition barrel for physical damage and test continuity; check connector for corrosion or loose pins.
- Monitor immobiliser/key recognition parameters with diagnostic tool: confirm key ID is read and that ECU/BCM exchange authorization messages over CAN.
- If key is not read, verify antenna wiring and repair/replace antenna as required. If key reads but ECU still inhibits start, check for CAN or module faults.
- If an ECU or BCM was recently replaced or had software update, verify immobiliser data pairing; reprogram or resynchronize keys using manufacturer procedures.
- If module hardware is suspected (faulty BCM or engine ECU immobiliser circuit), confirm with module bench tests or swap with known-good unit per workshop procedures before replacement.
- After repairs, clear codes and perform multiple start cycles to confirm repair; re-scan for reoccurrence.
Likely causes
- Damaged or unprogrammed key (most common)
- Antenna coil failure or loose connector at ignition switch
- CAN communication error between security module and ECU
- Recent replacement of ECU or BCM without re-pairing keys
- Intermittent power/ground to immobiliser module
Fault status
Status
Engine immobiliser function — key validation or immobiliser communication fault detected; engine start may be inhibited.
Repair difficulty: Hard
Diagnostic time: 0.5-3 hours
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