P1612 – Chain of ECM-IMMU (Nissan/Infiniti)

Brian Jones

By Brian Jones (Contact Me)
Last Updated 2019-02-22

Trouble CodeFault LocationProbable Cause
P1612 Engine Control Module Coding (AUDI, VOLKSWAGEN)
Loss Of IPM Serial Data (BUICK, CADILLAC, CHEVROLET, GMC)
Immobilizer Malfunction (HYUNDAI)
Chain of ECM-IMMU (INFINITI, NISSAN)

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What Does Code P1612 Mean?

This code signifies an interruption of communication between the ECM and the IMMU. As a result, the engine will not start. Often, it’s simply related to using the wrong or damaged key while other instances might point to an issue with the ECM or immobilizer.

Nissan and Infiniti both use anti-theft and immobilizer systems with this function. Components consist of:

  • Engine Control Module (ECM)
  • Security indicator lamp
  • NATS antenna amp
  • Body control module
  • NATS ignition key

What are the common causes of code P1612?

Occasionally, this occurs during the key registration procedure and the code remains stored. More commonly, this code is triggered because of an unregistered key that’s used five times consecutively.

Other known causes include:

  • Open circuit in battery voltage line of IMMU circuit
  • Open circuit in ignition line of IMMU circuit
  • Open circuit in ground line of IMMU circuit
  • Open circuit in the communication line between ECM and IMMU
  • Short circuit between ECM and IMMU communication line and battery line
  • Short circuit between ECM and IMMU communication line and ground line
  • Faulty IMMU
  • Faulty ECM

What are the symptoms of code P1612?

  • Engine Light is on
  • Engine will not start

How difficult is it to repair code P1612?

There’s no way to reprogram the key without dealer tools. If it’s an issue with a loose connection, once the fault is found, repairing it only takes a few seconds.

How do you troubleshoot code P1612?

  1. First, look at your key. If it is the wrong key or is damaged, you need to get a new one from the dealer.
  2. Disconnect the battery for 30 minutes and then attempt to start the engine again.
  3. Check for a blown fuse.
  4. Check the voltage between the connector and body ground to see if there’s an issue in voltage with the immobilizer.
  5. Check the voltage between the terminal and body ground. Make sure the ignition switch is turned on. This indicates an issue with the immobilizer.
  6. To look for an issue with the ECU, you would need special equipment to check the condition.

Codes Related to P1612

  • P0606 PCM / ECM Processor Fault
  • P1570 Engine Control Module Immobilizer Active
  • P1610 NISSAN – Lock Mode
  • P1611 NISSAN – Key ID Discord IMM-ECM
  • P1613 NISSAN – ECM INT CIRC-IMMU
  • P1614 Chain of IMMU-KEY
  • P1615 NISSAN – NVIS Difference of Key

Often, P1612 and P1614 will present themselves together. This is common and often indicates a problem larger than with the key itself.

Other Manufacturer Specific Definitions for P1612

Loss Of IPM Serial Data (GM)
Engine control module (ECM) - coding (Volkswagen)
Engine control module (ECM) - coding (Audi)
Loss Of IPM Serial Data (Buick)
Instrumentation control module (Cadillac)
Loss Of IPM Serial Data (Chevrolet)
Throttle position (TP) control module malfunction (Chrysler)
Engine control module (ECM) -supply voltage (Dodge)
Engine control module (ECM) -supply voltage (Freightliner)
Immobilizer Malfunction (Hyundai)
Immobilizer control module/engine control module (ECM) communication – malfunction (Infiniti)
Immobilizer control module/engine control module (ECM) communication – malfunction (Nissan)
Electronic throttle system (ETS) – no signal (Volvo)

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