Code
P1612
DS
P — Powertrain
Engine immobiliser function
Views:
UK: 1
EN: 5
RU: 2
AI status
Completed
Completed
100%
Causes
- Key transponder (remote/key) not recognised or damaged
- Immobiliser antenna/reader (coil) or its wiring/connector fault
- Immobiliser control unit/module internal fault
- Loss of power or ground to immobiliser unit (blown fuse, poor connection)
- CAN/K-Line communication fault between immobiliser and engine/PCM
- Aftermarket alarm or RF interference preventing key recognition
Symptoms
- Engine does not start or cranks but will not run
- Immobiliser/engine security warning lamp illuminated or flashing
- Starter cuts out immediately after cranking or fuel pump does not prime
- Intermittent starting or no recognition of one or more keys
- No communication with immobiliser module reported by scan tool
What to check
- Read DTC(s) and freeze‑frame data with a capable diagnostic tool; record all related stored codes
- Try to start vehicle using a known-good spare key (verifies key transponder)
- Observe immobiliser/service/security indicator behaviour during key insertion/starting
- Check battery voltage and main fuses related to immobiliser and ignition
- Inspect wiring and connectors at ignition barrel/reader, immobiliser module and PCM for damage or corrosion
- Scan for communication (U‑codes) on CAN bus and check for related module faults
Signal parameters
- Immobiliser antenna coil continuity/resistance and voltage supply to antenna (manufacturer‑specific values)
- Transponder reader detection/handshake events (key recognized/not recognized)
- Immobiliser status flags/messages on CAN/K‑Line between immobiliser unit and PCM
- Ignition switch/reader input voltages during cranking (battery voltage under load)
Diagnostic algorithm
- Connect a diagnostic scanner and read P1612 and any other stored codes; capture freeze‑frame and event data
- Verify vehicle battery is charged and supply circuits (fuses/relays) to immobiliser and PCM are intact
- Attempt start with a known-good spare key; note any difference in behavior
- Observe immobiliser/security warning lamp and use diagnostics to request key recognition status
- Visually inspect antenna/reader around the ignitor or PUSH BUTTON receiver and associated wiring and connectors for damage or corrosion
- Measure antenna coil continuity/resistance and supply voltage to the antenna per manufacturer spec (if available)
- Check power and ground at the immobiliser control unit and verify module presence on CAN/K‑Line with a scope or diagnostic tool
- Scan network for communication faults (U‑codes); if communication is lost, trace wiring and network connections
- If key is not recognized but hardware checks OK, attempt manufacturer procedure to re‑synchronise or reprogram keys using dealer-level diagnostic tool
- If immobiliser or ECU was recently replaced or updated, verify correct module coding and software levels; perform software updates if recommended
- Replace faulty component (key, antenna, immobiliser module) only after confirming fault; clear codes and test drive to confirm repair
Likely causes
- Damaged or worn key transponder (most common)
- Faulty antenna/reader around ignition barrel or push‑button receiver
- Poor power/ground or blown fuse to the immobiliser module
- Communication failure between immobiliser module and engine ECU (CAN bus)
Fault status
Status
Engine immobiliser function fault — immobiliser has prevented normal engine start or key authentication failed.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
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