NATS Immobilizer & No-start: P1610, P1614
I wanted to share something that happened one day last week.
Upon trying to start my car, it cranked with good-sounding intent, but never actually started. There were no prior warning symptoms or a lit MIL earlier in the day. In fact, everything has been running great for the past few months. After trying to start it several times, I noticed that while the key/ignition was in the "ON" position, the immobilizer light was in a constant-on state. From what I've seen, the light should only remain on for about a minute when initiating a lock and closing all doors.
The key I was using, a TK40 NS34U replacement, was cut and programmed from my original. I used this key as my primary for at least 6 months without issue. That day, it apparently stopped working. After waiting about 20 minutes, I tried using the original factory key, and the car started on the third try with it. I later pulled codes P1610 and 1614. Both P1610 and P1614 indicate a NATS (anti-theft system) malfunction, yet P1610 is a resulting DTC from the "LOCK MODE" condition which is set for various NATS malfunctions or an improper key being used. It prevents the car from starting (for some period of time, even if the key issue is rectified). P1614 merely indicates an issue with the anti-theft system because the IMMU cannot receive the key ID signal.
To reset a NATS lock mode, a proper key must be cycled three times again to get the car to start, explaining why with even using the original key, it took three tries to start.
For now, I'm assuming that the key transponder in the replacement key became damaged or corrupted somehow. I have not had issues since using the original key again.
If anyone has some input with NATS issues, feel free to add some information here. I just wanted to share this for those who experience no-start issues and go replacing every possible sensor with no solution.