Chevy Express Service Theft Deterrent System: Causes + Reset Procedure

Most GM vehicles built in the last 20+ years have a theft deterrent system, that includes the Chevy Express.  Depending on the model year, your van’s theft deterrent system disables the fuel pump, ignitions system, or starter if unauthorized access is detected.  

When your vehicle Express theft deterrent system message, the system will not let the vehicle start. Resetting the system takes about a half hour and is something you can often do yourself at home.

Chevy Express Service Theft Deterrent System

The two most common causes of “Service Theft Deterrent System” are a bad battery or a new/faulty key.

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Chevy Express Service Theft Deterrent System Causes

Service theft deterrent system causes Chevy Express

Here are the most common reasons the service theft deterrent system warning can occur in the Chevy Express.

Dead Battery

If your Express has a low or dead battery for an extended period, it can mess with the theft deterrent system.

A weak battery or discharged battery won’t make it through the half-hour-long process of resetting your service theft deterrent system (detailed in the next section).

Newly Cut Key

If you have a new key cut for your Express, it can trigger the service theft deterrent system message.  You’ll need to turn the key and wait for the theft deterrent system to learn it.  Jump down to the next section for exactly how to do that.

Other Causes

Other causes of the service theft deterrent system message include a bad key fob, a blown security system fuse, or ECM issues.

How to Fix “Service Theft Deterrent System”

There is a way to get rid of the service theft deterrent system message on most modern GM vehicles.  Here’s what to do:

  • With a fully charged battery, put the key in your Express’s ignition and turn it like you are going to start the engine.  Leave the key in the on position. You’ll see the little padlock symbol, security light, or service theft deterrent system message.
  • Once the padlock goes out (takes about ten minutes), try and start your Express.
  • If you repeat this process three times, the key should start working, and the padlock symbol should disappear.

What is a Theft Deterrent System?

GM’s theft deterrent system goes by the name “PASSlock,” or just the theft deterrent system. However, no matter what name it goes by in your Chevy Express, it still functions in the same basic way.

A theft deterrent system is designed to make your van harder to steal.  It is an alarm system, and it’s an immobilizer (makes it where your Express won’t start). The service theft deterrent system warning won’t make your Chevy Express’s alarm go off randomly, but it won’t be able to start.

Given enough time, almost any security system can be bypassed.  A security system aims to alert you and make the hassle of stealing your van and possessions too great for the potential thief.

Parts of a Theft Deterrent System

Depending on the model year, your Express will have some variation of the parts and sensors listed below.

  • Immobilizer– An immobilizer is an anti-theft device installed in a vehicle. It uses electronic chips embedded in the key to send a signal that the car’s computer must recognize before it will start. This prevents unauthorized people from being able to start the vehicle and steal it.
  • Vehicle Sensors– Newer, modern security sensors on a vehicle include motion sensors, which are triggered when the vehicle is moved; tilt sensors, which detect any change in the angle of the vehicle; and proximity sensors, which detect when someone is too close to the car. Additionally, infrared sensors can detect when a key fob is within range of the Chevy Express and will only unlock the doors if the right signal is sent. Hood latch, door lock, and key recognition sensors have existed for decades.
  • Key Fob– Key fobs are an essential part of vehicle security, as they use advanced electronic chips embedded in the key to send a signal that must be recognized by the van’s computer before it will start. This ensures that only authorized users can unlock and start the vehicle, protecting it from theft.

What Does Service Theft Deterrent System Mean?

The Service Theft Deterrent System is an alert message that a Chevy Express owner may receive when their anti-theft system is not functioning properly.  The two most common causes for it are a dead battery and key issues.