New here with a question? Go easy on me.
 

I have a 2003 Nissan Maxima I am experiencing a strange issue I can't solve. I replaced my ECU, immobilizer, had keys programmed by lock smith, so I did this because I fried my ECU and lost my keys, now when I try to start my car the red NATS light is solid I perform lock out procedure, then it starts go down the road the AT check light comes on and the car dies, try to restart it cranks, but do not start the NATS light is solid and AT check light starts to flash. I do not have a check engine light on. I need help. This is an ongoing issue. Thanks

Did the new ECU, immobilizer and keys come from the same donor car?
After the keys were programmed by the locksmith, I assume it started right up just fine? Was the car turned on and off repeatedly to confirm successful programming?

Thanks for your prompt reply the Wizard. No. the ECU came from a donor, but I bought the immobilizer from Nissan and yes after the keys were programmed the car started right up repeatedly with both set of keys, which I purchased from Nissan.

The Wizard thank you for your reply. The immobilizer did come from a donor, but I bought the immobilizer from Nissan after the locksmith programmed the keys, both keys started the car repeatedly.

sounds like a failing immo, b/c they act flakey

At this point, would've been better to just pay for the reflash with NATS removed.

Thanks for your prompt reply the Wizard. No. the ECU came from a donor, but I bought the immobilizer from Nissan and yes after the keys were programmed the car started right up repeatedly with both set of keys, which I purchased from Nissan.

I had a simalar problem with my 2002 about 8 years ago. Car would crank but no start no matter after many attempts. I put my OBD scanner indicated it was an alarm problem. The immobilizer "acted" like someone was trying to steal the car. I spoke to several local shops. They all stated that they cannot fix or program any keys. They said it needed to go to Nissan and diagnosed with their "CONSULT". OK then, had it towed to Nissan they changed out or fixed immobilizer and reprogramed the keys.

Total cost $538.00. That was 8 years ago. That was the only time Nissan worked on my car with 22 years of ownership.

I also took the vehicle to the Nissan dealer and they programmed a new set of keys the car ran fine until recently. I changed the immobilizer and had a lock smith reprogram the keys after I changed the immobilizer, the keys started the car multiple times, so I assumed that fixed the problem, it did not, should I have let the Nissan dealership reprogramed the keys, after the immobilizer change that I bought from Nissan. There is no communications with the car. I tried to scan for codes, but no communication with the car. By the way I fried my original computer and bought another from Flagship, this is the computer I am dealing with, it also have a life time warranty.

You can program the keys yourself, but if they're not sticking, it sounds like IMMO. Nissan Data Scan 2. Stealerships are never to be trusted.
Check ecu fuse, maybe it doesn't have power (for whatever reason).

Would the key cause the computer to not communicate? Where would I purchase the tool to program the keys?

UPDATE.. It turned out to be a loose wire on my Engine control relay. I removed the relay and tightens all the connectors and what you know, the solid security light went out and the AT check stop flashing, and the computer started communicating again and the car fired right up. Thanks for the feed back, but I think I may need a fuel pump, where is the best place to purchase one?

I changed my fuel pump about 5 years ago on my 2002. I purchased IMPORT DIRECT, car runs perfect. I think I got it from Rock Auto or Auto parts warehouse. Which is now carparts.com.

Make sure you disconnect Battery when doing this job. You don't want any accidental spark igniting while pulling pump from gas tank............