P1612

CHAIN OF ECM-IMMU

System Description
IVIS (Infiniti Vehicle Immobilizer System - NATS) will immobilize the engine it someone tries to start it with- out the registered key of IVIS (NATS). Only IVIS (NATS) ignition keys with ID numbers that have been registered into the ECM and the IMMU allow the engine to run.
A malfunction that triggers this code may turn the security indicator ON to make the engine hard to start. If the security indicator illuminates with the ignition key ON or the engine running, it may indicate that there is an abnormality in the system. For this condition perform SELF DIAGNOSIS.
It is normal for the security indicator to blink when the ignition switch is in OFF or ACC.
IVIS (NATS) trouble diagnoses, system initialization and additional registration of other IVIS (NATS) ignition key IDs must be carried out using CONSULT-II hardware and CONSULT-II IVIS (NATS) software.

On Board Diagnostic Logic
Communication impossible between ECM and IMMU
In rare case, "CHAIN OF ECM-IMMU" might be stored during key registration procedure, even if the system is not malfunctioning.

Possible Cause
- Open circuit in battery voltage line, ignition line or ground line of IMMU circuit.
- Open circuit in the communication line between IMMU and ECM.
- Short circuit in the IMMU/ECM communication line to battery voltage line and/or ground line.
- The IMMU is malfunctioning.
- The ECM is malfunctioning.

Diagnostic Repair Procedure (for confirmed incidents)
1. Check power supply and ground for IMMU.
2. Check communication line between ECM and IMMU:
Disconnected, ignition key ON, Continuity/No shorts to ground or power
3. Check ECM communication interface:
Connect ECM connector and check the signal from ECM to IMMU with CONSULT-II or oscilloscope when ignition switch is turned "ON".




- If NG, replace ECM (see part B in illustration). Then perform initialization with CONSULT-II.
- If OK, replace IMMU (see part A in illustration). Then perform initialization with CONSULT-II.


Diagnostic Repair Procedure (for unconfirmed incidents)
1. Run engine; select SELF DIAGNOSIS with CONSULT-II; perform "Wiggle Test" on all related connectors.
2. Inspect all related harnesses, connectors and pins.


Symptom Matrix Chart