P1611

NATS ID Discord, IMMU-ECM

Car Fault Codes Nissan Engine computer & electrical

Can you still drive? No, stop right away

Who can fix it? Needs a specialist or dealer

Typical repair time 30 minutes – 4 hours

Typical cost SAR 250 to 5,000

What it means

This is a Nissan-specific code for vehicles with NATS; the same number can mean something different on other makes. It means the ID held by the immobilizer unit (IMMU) does not match the ID registered in the engine computer (ECM), so the ECM refuses to allow the engine to run. It usually appears after one of the two was replaced with a used or new part without performing the registration (pairing) between them.

Models covered: Nissan (and Infiniti) models with NATS (Nissan Anti-Theft System), mainly around 1999–2008 (e.g. Altima, Maxima, Sentra, Pathfinder, X-Trail).

Symptoms4

The engine does not start, or starts and stalls after a moment.
The security indicator light stays on with the ignition on.
The fault appeared after replacing the ECM or immobilizer unit, or after electrical work.
All keys give the same result, because the problem is not in one particular key.

Possible causes5

A used or new ECM installed without pairing it to the immobilizer unit.
A replacement immobilizer unit installed without registering it to the ECM and keys.
An incomplete or interrupted registration due to low battery voltage during programming.
Corrupted data stored in the ECM or the immobilizer unit.
An internal fault in the ECM or immobilizer unit (less common).

How to diagnose5

Ask about any recently replaced part; an ECM or immobilizer unit swap is the most common cause.
Confirm the battery is healthy and its voltage is stable before any programming.
Read all codes with a Nissan-capable scan tool and check for communication codes such as P1612.
Verify by part number that the installed ECM is correct for the model and engine.
Perform the NATS initialization and key registration, and check whether the code clears.

How to fix6

Charge the battery or hold its voltage with a suitable charger before programming.
Perform NATS initialization to pair the ECM with the immobilizer unit using a Nissan-capable tool; this may require the vehicle's security code.
Register all keys again after pairing.
Refit the original ECM if it is healthy and the replacement was not needed.
Replace the ECM or immobilizer unit if confirmed faulty, then program and pair it.
Clear the codes and start the engine several times to confirm the repair holds.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low when pairing and key registration with a Nissan tool are enough, and rises sharply if a new ECM or immobilizer unit with dealer programming is needed.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

I installed a used ECM and got this code. Why?

Every ECM holds an ID tied to the immobilizer unit of its original car, so it must be paired with your car's unit and the keys registered using a Nissan-capable tool.

Will a new key fix this?

Usually not. The mismatch is between the immobilizer unit and the ECM, not between the key and the unit, which is why every key gives the same result.

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This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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