1990-1993 Infiniti Q45 Anti-Theft Module: Solving No-Start Issues with a Plug-and-Play Fix

Symptoms of a Failing Anti-Theft Module

When the anti-theft module in a 1990-1993 Q45 begins to fail, the symptoms are usually straightforward and can be mistaken for a bad starter or battery. The most common signs point to the module incorrectly preventing the car from starting.

• Engine Will Not Crank (No-Start): This is the most definitive symptom. You turn the key, the dashboard lights come on, but the engine does not turn over at all. This happens because the faulty module is keeping the starter inhibit relay activated, blocking the signal to the starter motor.
• Intermittent No-Start: The problem may start intermittently. The car might fail to start once, then work perfectly for several days before the issue returns. This can be caused by failing internal components like solder joints or capacitors inside the module.
• Security Light Stays On or Flashes Incorrectly: The small red "SECURITY" light on the dashboard may behave erratically. It might stay illuminated even when the car is running or flash when it shouldn't, indicating a fault within the system.
• Alarm Sounds Randomly: A less common symptom is the car alarm activating for no reason, even when no doors have been opened. This points to an internal short or a faulty logic board within the module.

Buying a Used 1990-1993 Q45 Anti-Theft Module

Since new OEM modules are no longer produced and aftermarket options are non-existent, a quality used OEM module is the only practical solution. Here’s what you need to know to buy with confidence.

The #1 Benefit: No Programming Required

The most important thing to understand is that the security system on the 1990-1993 Q45 is a simple starter-kill system. It does not use a chip-based key immobilizer (like the later Nissan Anti-Theft System, or NATS). This means a replacement module is 100% plug-and-play. You do not need to take the vehicle to a dealer or locksmith for programming. Simply install the replacement module, and the system will function correctly. This makes a used module an excellent, cost-effective repair.

How to Ensure Compatibility

1. Match Part Numbers: The known OEM part numbers are 28590-60U00 and 28590-60U10. The number 28590-60U10 is likely a later revision or replacement for the original. While they are expected to be interchangeable, matching your original part number exactly is always the safest bet. The part number is printed on a sticker on the module's case.
2. Physical Inspection: When you receive the used module, inspect the case for any signs that it has been opened. Check the connector pins for corrosion, rust, or damage. Water intrusion is a common enemy of electronics, so any sign of moisture damage is a major red flag.
3. Why Used OEM is Your Best Choice: For a vehicle of this vintage, a used OEM part is superior to any theoretical aftermarket alternative. The original Infiniti part was designed for perfect fitment and integration with the vehicle's wiring. Since no programming is needed, there is no downside to using a tested, working module from a donor vehicle.

Known Issues, Recalls, and TSBs

There are no specific recalls or Technical Service Bulletins (TSBs) issued by Infiniti or the NHTSA for the anti-theft control module on the 1990-1993 Q45. The system is known to be relatively basic; for instance, it does not include a shock sensor, so the alarm would not sound if the wheels were stolen without a door, hood, or trunk being opened. Failures are typically due to the age of the electronic components rather than a specific design flaw.

Replacement Guide

Replacing the anti-theft module is a manageable DIY task for those comfortable working under the dashboard.

• Location: The anti-theft control module is located behind the dashboard on the passenger's side (Right Hand side). You will likely need to remove the glove box assembly to gain access.
• Tools Required: Basic hand tools, including a Phillips head screwdriver and a socket set (likely 10mm), are usually all that's needed.
• Steps:
  1. Disconnect the negative terminal from the car battery.
  2. Remove the glove box door and the surrounding trim panels as needed to access the area behind it.
  3. Locate the module. It is a small plastic box with one or more wiring harnesses connected to it.
  4. Unplug the electrical connectors. Be gentle with the plastic tabs, as they can be brittle after 30+ years.
  5. Unbolt the module from its mounting bracket and remove it from the vehicle.
  6. Installation is the reverse of removal. Mount the new module, plug in the connectors, reassemble the dash, and reconnect the battery.

Frequently Asked Questions (FAQ)