A Nissan vehicle that cranks but won’t start can be incredibly frustrating. Often, the culprit is a malfunction within the Nissan Anti-Theft System (NATS), also known as the Nissan Vehicle Immobilizer System (NVIS). This article will delve into troubleshooting a no-start condition potentially caused by a Nissan Nats Malfunction, using a real-world example of a 2001 Nissan Sentra SE with a 2.0-liter engine.
Understanding the Nissan NATS System
The NATS system is designed to prevent vehicle theft by disabling the engine unless the correct key is recognized. This system uses a transponder chip embedded in the key that communicates with the vehicle’s immobilizer control unit. If the communication fails or the key isn’t recognized, the engine won’t start. Common indicators of a NATS issue include pending trouble codes P1610 and P1612, which directly relate to immobilizer system malfunctions.
Diagnosing a NATS-Related No-Start
In the case of the 2001 Sentra, the owner experienced a sudden no-start condition after the car had been running fine. Initial troubleshooting steps included replacing the weak battery, checking for diagnostic trouble codes (DTCs), and confirming the absence of spark. Two pending codes, P1610 and P1612, pointed towards a potential NATS issue.
Further investigation revealed that the fuel pump seemed to be functioning, albeit not definitively confirmed. Manipulating the key (on/off cycles, trying different keys) and disconnecting the battery did not resolve the issue. Notably, the remote key fobs functioned for door locks but not for the trunk, a potential clue to a broader electrical or immobilizer system problem.
The vehicle’s security indicator light provided further insights. It blinked once every 30 seconds, less frequently than the expected three-second interval for a normally functioning system. Turning the key directly to the crank position kept the light off, while turning the key to the ‘on’ position and waiting five seconds caused the light to stay on continuously, even during cranking.
A locksmith, consulted twice, initially dismissed the immobilizer system as the cause. However, subsequent tests with specialized equipment yielded inconclusive results. The owner then delved into the factory service manual, performing various checks on the crankshaft position sensor, ignition system components (distributor, coils, cap, rotor), and the NATS system itself. These tests included:
- Crankshaft Position Sensor: Resistance within the specified range and RPM signal detected during cranking.
- Ignition System: Primary and secondary coil resistance checks, power transistor test, distributor cap resistance check. Some readings were slightly out of spec, but not significantly.
- NATS System: Power supply and ignition switch signal checks at the NVIS IMMU connector.
Next Steps and Considerations
Despite extensive troubleshooting, the root cause remained elusive. The conflicting evidence between the NATS codes and the locksmith’s initial assessment presents a challenge. Key takeaways include:
- Don’t dismiss DTCs: Pending codes P1610 and P1612 strongly suggest a NATS issue and should be thoroughly investigated.
- Consult reputable sources: While a locksmith can be helpful, referencing factory service manuals provides crucial information and specific test procedures.
- Systematic approach: A methodical approach to diagnostics, following a logical flow chart and utilizing proper testing equipment, is essential.
Conclusion
A Nissan NATS malfunction can lead to a no-start condition that requires careful diagnosis. While this case study didn’t pinpoint the exact cause, it highlighted the importance of understanding the NATS system, correctly interpreting diagnostic trouble codes, and performing systematic troubleshooting steps. If you suspect a NATS issue in your Nissan, consult a qualified technician with experience in diagnosing and repairing these systems.
