[NATS] Nissan - no start after reversed battery polarity and ECU repair

I have the following situation:

A few years ago, my father bought a new key from a Nissan dealership. At first, it didn't work, so he returned to the dealership with the car. After that second visit, the new key was able to start the engine.

Some time later, that key was lost. My father then had a new key made by a locksmith, but it did not contain an immobilizer transponder chip. To his surprise, one day he tried this chipless key and discovered that it was also able to start the car.

The story continues.

A few years later, the ECU was damaged and replaced by a technician at an independent garage. Even after the ECU replacement, the chipless key continued to start the car without any problems.

A few weeks ago, the car was left at a body shop for painting. As part of the work, the battery was removed and remained disconnected for approximately three weeks. When we went to collect the car, the engine would no longer start. The car was then transported to another garage for diagnosis.

The diagnostic tool initially reported either a camshaft position sensor fault or an immobilizer fault. The camshaft sensor was replaced, but the engine still would not start. The garage then asked an ECU specialist to inspect the ECU, and he concluded that it had been damaged. There was also evidence that the battery polarity had been reversed, which could explain the ECU failure.

The ECU was sent to a repair specialist, who successfully repaired it. However, despite the repair, the engine still does not start.

Because the battery polarity was reversed and the complexity of Nissan NATS system it seems that nobody knows what to diagnose and repair on the car.

Can someone please help with some direction to follow?
AI: What is the exact Nissan model, year, engine type/code, market/region, and ECU part number or photo of the ECU label?
Almera N16 G; G05 1.5 Petrol, 2002 Europe, Portugal
The ECU has this label on top:
MEC20-601 ZQ
MEC20-601 B1 1Y05

On the side there's:
MEC20-601 B1 A2417

But the original ECU was replaced by this one, so we are not sure that the labels are correct...

Fact that the car ran for years with a key that had no transponder strongly suggests the ECU previously had NATS (immobilizer) disabled. My guess is that during the ECU repair, original file was replaced with a stock one, re-enabling the immobilizer. I'd start by confirming whether the ECU still has immo off or if it now requires NATS synchronization with the immobilizer module and keys.

Hello,

After some more investigation, it was possible to find the transponder glued to the immu antenna. So this situation is clearer. :-)

Now we only have error P1610 Lock Mode.
It seems that we will need to sync the key+transponder with the ECU, but we need a PIN.

Can someone help us to get the PIN?
Here you have the IMMU picture.


Thank you very much for the huge help!

Probably the simplest solution Link

Hi Carrot,

Thank you very much!

I've been searching for an ECU + IMMO kit for a while now, but even finding just the ECU has been very difficult. This car uses a MEC20-601 ECU.
I'm also trying to find an official Nissan dealer that still has a Consult II, but that's proving difficult as well.

Do you know if a MEC20-601 ECU with an emulator would bypass or solve the NATS lock mode? At this point, I think that's the only option I have left.

Hi Carrot,

Your post encouraged me to make one last special effort to find a kit, even though every used-parts shop I contacted told me it would be impossible to find one, as they don't usually keep those parts together. 🙏🏼

So on the next day in the afternoon, I went to what could be called the used-parts town near Lisbon (an area in Sacavém), and the second shop I visited turned out to be "the only one" that keeps the parts together and sells them as kits. 😯

However, the salesman told me that he had experienced exactly the same issue with the same car and had also been unable to start it with a kit. So he wasn't willing to take any responsibility and sold me the kit for an amazing price. 🤩

And the day after, with the new ECU + IMMO + BCM + transponder, the P1610 error was gone and the car started! It was initially pretty unstable and wouldn't stay running, so I needed to have the injection maps copied from the old ECU. After that, the car has been running perfectly after 1,000 km. ♥️

For others experiencing the same issue, this may be the way to go. Even if you have access to Consult or another diagnostic machine, this option could be cheaper, faster, and ultimately more reliable.

I would also like to share that the issue with the injection maps occurred even though the replacement ECU had exactly the same reference - ZQ MEC20-601 B1 - with only the last four alphanumeric characters (XXXX) being different.

I also lost the radio, as it is now stuck displaying "SECURE". It seems that the radio should also have been matched/replaced as part of the kit, but since I rarely use it and it can easily be replaced in the future with an even better media solution, that's not really a problem.

Without your post, I probably wouldn't have continued searching for a kit, and I wouldn't have had the chance to go on vacation.

So thank you very, very much! 🙏🏼🙏🏼🙏🏼

All the best,
David.

I got help to go on the right direction.