I bought a 2005 G35 Coupe this week last year and the immobilizer has been giving me problems since the day I bought it. I test drove it, ran great, and bought it; then the same night I got locked out by the immobilizer system which prevents the car from starting (red dot stays solid on security light to the left of steering wheel). The problem became evident and after a week or so of owning it I took it to the Infiniti dealership, where they assured me I just needed new keys because the dealership gave me one regular key and one aftermarket key. I paid for the new keys and reprogramming for them which the dealership kindly reimbursed me for. After I picked the car back up, the car kept locking me out. I did a lot of research and ended up taking it back to the dealership. The dealership then told me the only other problem could be the NATS antenna that reads the chip in the keys because it had to be malfunctioning. I bought the antenna and then picked it up a few days later where the service rep told me he personally started the car dozens of times and they didn't have any trouble starting it. I took the keys and pulled to the front of the dealership to get my stuff out of the loaner, and then the car locked me out again in the parking lot. I left the keys with the service rep and he said it had to be a problem with the BCM. When I returned to the dealership he basically told me they ran tests on the BCM while starting the car hundreds of times and never came up with any error messages, and then gave me my keys back. I had owned the car about two months at this point and October was coming up which meant Atlanta temperatures were finally dropping. While I was considering calling other Infiniti dealerships farther away, the problem seemed to happen less and less often as it got cooler and cooler, and ended up going 7 months in a row without failing (I know this because I was keeping a log of the failures trying to recognize a pattern). Then in early May, seemingly when temperatures were rising again one day it just started happening again out of nowhere. I have no idea if temperature is related at all it just seems like an undeniable pattern of failing when it's hotter outside. It happened periodically throughout May and into June and early July it got worse and worse. It just so happens that when I moved houses over the winter I became neighbors with a head service tech at the nissan dealership in my area, and he told me to bring it in to have a look. When I brought it in they called me within an hour and told me they opened the immobilizer system and found water damage on the circuit board, I will attach pics. I was excited even when they told me the price of the replacement because it was something the Infiniti dealership never came across, and seeing it with my own eyes was undeniable. After all I had been through and paid for with Inifiniti, I was being told there was water damage on the circuit board of the system that had been malfunctioning for a year, and thought it had to be the answer. So I dropped the $650 on the new circuit board and picked up the car and it ran great all day, and then I got in the car that night to go out and it locked me out again. I was headed out of town the next day so I left it be and when I got back over the long weekend, I took the car to Publix and it ended up staying there until the next day, and then failing the next day again. I am calling Nissan in the morning to tell them and bring it back in, but it seems like so many professional service workers can't solve it. So has anyone had this problem and found the solution, or know what else I should be checking for damage?

 

Just a little out of the box thinking, maybe it's NOT the immobilizer but part of the neutral safety switch circuit preventing the vehicle from starting, if you have a manual transmission I would HIGHLY suspect the clutch switch since it's prone to issues. It's located at the top of the clutch pedal arm and has a plastic "stopper" that breaks off.

Are there ANY other keys on your keychain, you can have interference from another chipped key.

How old is your battery? I would have it hydro checked if it's not a sealed battery, if it is sealed and >5yr old I would just replace it to rule it out.

The NATS can be completely disabled by getting an UpRev tune btw. There's a user here (Seymore4) that can e-tune and there's usually an Uprev cable available on the marketplace for less than you would pay for a new one.

Do you try the immobilizer reset when you get the lockout?

1. Ignition off
2. Ignition on (do not start vehicle) wait 5 seconds.
3. Ignition off
4. Repeat steps 2-3 for 3 total cycles
5. Start engine

Also just to verify parts that have been replaced:

-Ignition Key
-Ignition lock cylinder and NATS antenna
-BCM

 

I have an automatic transmission, so not the clutch switch; with an auto transmission is it still possible to have problems with the neutral safety switch circuit?

Yes, I've tried the immobilizer reset a thousand times and then some, and I have no other chips on my key ring or in my car, made sure of that a long time ago.

Not sure when the battery was last replaced, I bought it with the battery that is in it now. Do you think even if the battery was the problem it would be triggering the immobilizer system like that? Anytime it locks me out I have the solid red security light, and both dealerships I have been to have seemed to agree it had to be something to do with that system, but I'm ready to try anything at this point.

And yes I have had the aftermarket key replaced so I have two Infiniti keys (pictures in the original post of them), and then had the keys reprogrammed. I got the NATS antenna replaced, and then most recently had the "immobilizer system's circuit board" replaced which I also included pictures of. On the invoice the description of the part I paid for is "IOG Amplifier", and I can find the invoices from the Infiniti dealership last year as well. I had the parts replaced in that order.