Why Does the Theft System Light Stay On in a 2001 Malibu?

by Justin Cupler

The 2001 Malibu cam relatively well-equipped with standard features. The mid-sized sedan came with: air conditioning, keyless entry, power door locks and a passive ignition disabling system. The passive ignition disabling system, known as Passlock, prevented the Malibu from starting without a coded key. When the Passlock system detects a fault in the security system, a "Theft System" light stays lit on the instrument cluster.

Incorrectly Coded Key

The Passlock system on the 2001 Malibu uses a key with a small magnet on it. This magnet passes a sensor inside the ignition tumbler, and the sensor reads the code stored in the magnet. If the codes do not match, due to improper coding or a failing key, the Theft System light stays on and the vehicle will not start.

Failed Ignition Tumbler

Over time, the wires inside the Passlock ignition tumbler can wear out and create a short. If the computer senses a short-to-ground in the wiring of the Passlock system, it triggers a "Security on" code that illuminates the "Theft System" light until you repair the problem.

Failed Instrument Cluster

As your 2001 Malibu ages, water and other debris can cause damage to the circuitry of the instrument cluster. If the instrument cluster shorts out, it is common for the "Theft System" light to illuminate.

Control Module Failure

The 2001 Malibu's body control module and powertrain control module work together to determine when the Passlock system is to allow the car to start. When one of these two components fail or are incorrectly programmed, the "Theft System" light illuminates and the Malibu will not start.

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