Passlock Relearn not Working [Causes & Fix]

Passlock is a popular anti-theft system used in many modern vehicles. It works by disabling the engine starter if an unauthorized key is used to start the vehicle.

However, the Passlock can sometimes become faulty and prevent the vehicle from starting even with the correct key. In such cases, I recommend relearning passlock as a troubleshooting step. 

But what happens when the Passlock relearn process doesn’t work? 

It could be a result of various reasons such as a faulty ignition switch.

In this case, your pass lock relearn will only function well if you have a qualified mechanic inspect and repair the ignition switch.

In this blog post, we’ll explore other reasons why the Passlock relearn process may not work and what steps you can take to resolve the issue.

Passlock Relearn not Working

What is a Passlock?

Just like we stated before, it is an anti-theft feature designed in GM vehicles to prevent unauthorized access.

This system uses a small electronic module located in the ignition lock cylinder to authenticate the keys used to start the engine. 

The system works by comparing the resistance values of the key to a pre-programmed value stored in the Passlock module.

If the values match, the Passlock system allows the engine to start. If the values don’t match, it will disable the fuel injectors and prevent the engine from starting.

Causes of Passlock Relearn not Working

1. Faulty Ignition Switch

The Passlock system is one of the many parts of the car that receives a signal from the ignition switch.

If the ignition switch is not functioning properly, it may not send the correct signal to the Passlock system, which could result in the system not being able to communicate with the engine management system. 

The Passlock relearn procedure may not function as a result because it depends on the system’s capacity to connect with the engine management system. 

Signs of a Faulty Ignition Switch

  • Difficulty turning the key in the ignition
  • The key getting stuck in the ignition
  • The engine not starting. 

If you suspect that the ignition switch is the cause of Passlock relearn issues, it’s important to have a qualified mechanic inspect and repair the switch as soon as possible to prevent further issues with the vehicle’s operation.

2. Failed Passlock Sensor

An essential part of the Passlock system, the Passlock sensor is in charge of detecting the key and communicating with the Passlock control module.

The ignition lock cylinder houses it, and it operates by sensing the resistance of the key. The sensor uses the resistance value that each key has to confirm that the right key is being used to start the car. 

If the Passlock sensor malfunctions, the Passlock system might be unable to communicate with the control module, which could lead to a failure of the relearn procedure.

The control module uses the sensor’s signal to determine whether the right key is being used; if the sensor is malfunctioning, it could prevent it from receiving the correct signal.

3. Malfunctioning Control Module

The Passlock control module is responsible for receiving signals from the sensor and communicating with the engine management system.

If the control module is malfunctioning, it may prevent the Passlock relearn procedure from working.

4. Worn-out Keys

Over time, the teeth on your key may become worn down or damaged due to normal use. When this happens, the resistance value of the key may change.

This can cause the Passlock system to not recognize the key as valid, preventing the engine from starting.

If the key is severely worn or damaged, it may not engage properly with the ignition lock cylinder, preventing the engine from starting.

If you suspect that a worn-out or damaged key is causing issues with the Passlock system, it’s important to replace the key with a new one.

You may also need to have the new key programmed to work with the Passlock system.

Regular maintenance and inspection of keys can help to prevent issues with the Passlock system due to worn-out keys.

It’s a good idea to inspect keys periodically for signs of wear and replace them as needed to ensure proper operation of the vehicle’s security system.

5. Incorrect Relearn Procedure

It’s important to follow the correct procedure when performing the passlock relearn procedure. If you follow the procedure wrongly, it may prevent the system from relearning the new key.

How to Troubleshoot Passlock Relearn not Working

1. Check your Key

Check the key to make sure it is not worn out or damaged. Because this could interfere with the sensor’s ability to read it.

Also, make sure the key is the right one for the car and isn’t a copy or duplicate. Use a new key if the key appears to be worn out or damaged.

2. Perform the Relearn Process

Performing the Passlock relearn process is a procedure that is designed to reset the security system in your vehicle. 

This process is necessary when the vehicle’s Passlock system has been activated and the engine is not starting.

It involves resetting the system and allowing the vehicle to relearn the key’s code so that the engine can start again.

How to Relearn a Passlock

  • Attempt to start the car before releasing the key from the “ON” position.
  • Keep an eye on the “SECURITY” signal light. The indicator “SECURITY” light will go out in ten minutes.
  • Press “OFF” on the ignition switch, then wait 10 seconds.
  • The vehicle has now learned the new password. Start the engine.
  •  Use a scan tool to clear any trouble codes.

Note that, for some cars, a single 10-minute cycle will be adequate to teach the car the new password. However, if your car won’t start after 1 cycle, perform all 3.

Also, make sure you charge your car battery fully before relearning your security system.

3. Check the Body Control Module

You must examine the body control module after the relearn procedure if it is unsuccessful. The usual method for doing this is to read the codes with a diagnostic scanner.

However, you can take your vehicle to a qualified mechanic who will be able to identify the problem if you don’t have the scanner or don’t know how to use it.

4. Replace the Damaged Parts

You may have to replace the damaged sensor in the ignition cylinder or the body control module if you discover that they are the source of the issue.

A certified mechanic or dealership can do this. To ensure proper fit and function, it’s crucial to use only the original parts.

5. Check for Software Updates

The Passlock system may occasionally experience software issues. If your specific model and year are subject to software updates, check with the dealership or the car manufacturer.

These updates can frequently resolve the Passlock system’s issues. To maintain the vehicle’s proper operation and security, it’s critical to keep the software updated.

6. Have your Vehicle Inspected by a Professional

If none of the previously stated steps succeeds in fixing the problem, then it is okay to contact a mechanic.

To identify and resolve the Passlock system’s issue, they will have the required equipment and knowledge.

They will be able to determine whether any additional underlying problems might be causing the Passlock system to act up.

You can have the car inspected to ensure that the issue is correctly identified and fixed to guard against the car experiencing more issues.

Read: How to Start a Car After Running Out of Oil


The Passlock relearn process is an important step in resolving issues with the Passlock system in vehicles.

However, if you have tried to perform the Passlock relearn process and it hasn’t worked as intended, there may be some underlying issues that need to be addressed. 

By understanding some common reasons why the Passlock relearns process may not be working, you can take steps to troubleshoot.

Therefore, whether it’s a faulty key or sensor issue, a trusted mechanic can help you find a solution that works for your vehicle.