GM PassLock Ignition Bypass

How To Permanently Disable A GM PassLock Anti-Theft System?

Car anti-theft and security systems are pretty underrated, especially when you consider how many times they probably saved your car from being stolen. Regardless, they’re not perfect, and every once in a while, they suffer faults or system failures that need fixing. But before you play around with it, it’s handy to know how to permanently disable a GM PassLock system.

There are many points of failure within General Motors’ PassLock system. Most of these are mechanical or electrical in nature. And, given how this system works, it’s the reason why a weak battery could cause your car to not start. At times, you might have frayed wires or worn wires, where a bypass alone might not solve the issues (depending on where it’s bypassed).

Thankfully, permanently disabling and bypassing a GM PassLock anti-theft system, regardless of the underlying issue at hand, is fairly simple. First things first, you’ll need to locate the PassLock theft deterrent module. You’ll notice that these are often housed in the ignition case, which is then attached to the steering column. Here’s how you can disable it…

Relearning The Anti-Theft System

Now, before we go through the nuclear option of trying to bypass or permanently disable a GM PassLock system, you might first consider re-learning the system first. These can sometimes help to solve minor glitches or hiccups in the system. It might even be enough to get you back into your car if the system wasn’t letting you do so beforehand.

For the PassLock anti-theft system to operate, a key must be in the lock cylinder. A revolving magnet and a stationary Hall Effect sensor are both present in the lock cylinder. The magnet generates a signal on the Hall Effect sensor when the key is turned in the lock cylinder. This then identifies your keys and authenticates the security system.

Your car’s body control module (BCM) or instrument panel cluster (IPC) is the recipient of the cylinder’s coded signal. The IPC/BCM will send a message over serial data to the PCM informing it that the car may be started if it receives the anticipated coded signal. To retrain a PassLock system, ensure that your car’s 12V battery is completely charged.

Without the alternator being able to recharge it, the battery will be used for 30 minutes. To ensure power that is constantly available when programming, connect a car battery charger to your car’s battery. The PCM and IPC/BCM must cooperate and communicate with one another. With that done, here’s how to relearn the GM PassLock anti-theft system:

Step-By-Step Instructions On Relearning GM’s PassLock System

  1. Start the engine.
  2. Turn the key to the “ON” position.
  3. Pay attention to the “SECURITY” light. The “SECURITY” indicator light will go out after 10 minutes.
  4. After waiting 10 seconds, turn the ignition to the “OFF” position.
  5. Try starting the car, then turn the key to the “ON” position.
  6. Observe the “SECURITY” indicator light. After 10 minutes, the “SECURITY” indicator light will turn off.
  7. Repeat it two to three times.
  8. The car is now familiar with the new password. Finally, you can start the car.
  9. Optionally, you can use an OBD scan tool to erase any error codes.

For most cars, a single 10-minute cycle will be sufficient to teach the car the new password. If the vehicle doesn’t start after one cycle, carry out all three. Some cars will need all three rounds to learn the password. These should help solve most glitches with the system. If that doesn’t work, you’ll need to permanently disable the GM PassLock system.

How To Permanently Disable & ByPass GM PassLock?

GM PassLock Ignition Bypass

If you’re having issues with your car’s anti-theft system and theft deterrent modules, here’s how to bypass and permanently disable the GM PassLock 3 system. Note, that this is for GM’s newer PassLock 3 system, whereas the older PassLock 1 and 2 systems, respectively, will continue down below.

  1. Take off the steering column’s top and bottom shrouds.
  2. Find the White, Black, and Yellow 3-wire ribbon cable that comes from the ignition switch. These wires are THIN.
  3. On the LEFT side of the steering column, directly above the ignition switch location, is the Black 6 position connector. The “Bulb Test” connector has a BLACK (Thin) wire that displays GROUND when the ignition is off, OPEN when it is in the “Run” position, and GROUND when it is in the “Crank” position.
  4. Position the ignition switch to “Run.” Do not start the engine.
  5. Strip both ends of the thin yellow wire.
  6. Make some of the copper visible without cutting the black wire.
  7. Measure the distance with an ohmmeter from the Yellow wire’s ignition switch end to the exposed Black wire and record the result. To ensure you get the correct value, take many measurements.

How To Disable & Bypass GM PassLock 1

PassLock 1 is mostly found on GM vehicles made before 2002. This anti-theft system uses a resistor pellet in the ignition key and a decoder module (TDM) that recognizes the resistance value to enable the starting of the vehicle. Here’s how you bypass and disable the GM PassLock 1 system:

  1. Determine Resistor Value: Start by measuring the resistance of the pellet in your key. You can do this using a digital multimeter. Now, hold one lead on one side of the pellet, and the other lead on the other side.
  2. Purchase Resistors: Get yourself a resistor of the same resistance value as the one in your key, and an additional 2.2k Ohm resistor.
  3. Access PassLock Wires: Take off the steering column’s cover, and locate the three-wire PassLock sensor connector.
  4. Bypass PassLock Sensor: Cut the yellow wire (or the thin yellow wire, if there are two yellow wires) and the black wire, leaving some length on the wires to work with. Connect the end of the yellow wire from the ignition switch to one side of the resistor you bought, and the other side of the resistor to the black wire.
  5. Connect 2.2k Ohm Resistor: Connect the 2.2k Ohm resistor across the two wires going to the PassLock sensor.
  6. Test the System: Finally, try to start your car. If the security light goes out, it means the system has been bypassed successfully.

How To Disable & Bypass GM PassLock 2

PassLock 2 is an upgrade from PassLock 1. You’ll find that they’re more common in vehicles made from 1995 to 2008. It works on a similar principle as PassLock 1, but uses a hall-effect sensor instead of a resistor pellet. Here’s how you can disable and bypass the GM PassLock 2 system:

  1. Locate PassLock Wires: Start by taking off the steering column’s cover and locating the PassLock sensor wires. You’ll notice that these are usually three wires colored yellow, black, and white.
  2. Cut the Yellow Wire: Cut the yellow wire, which is the data wire. The vehicle won’t start with this wire cut, and the security light will flash.
  3. Wait for Security Light: Wait for the security light to stop flashing, which usually takes about 10 minutes.
  4. Connect the Yellow Wire: After the security light stops flashing, connect the yellow wire back together. The vehicle should now start and stay running.
  5. Permanent Bypass: To make the bypass permanent, connect a 2.2k Ohm resistor across the cut yellow wire. This will trick the system into thinking it is receiving the correct signal from the PassLock sensor.

REMINDER: Remember that disabling the anti-theft system can make your car more attractive to thieves. It is advisable to have some other form of anti-theft device installed if you choose to disable the PassLock system. This can be a steering wheel lock, a kill switch, or an aftermarket alarm system. Also, just for reference, here’s a pic of what the ignition system looks like:

GM PassLock Ignition Bypass


  • Michael Dornseif Says

    Hello, I have a 99 Silverado having passlock issues. After I got it running I cut yellow signal wire near ignition switch so it would have a fault while running issue now,that bypasses passlock now on start up. Question is will it reset passlock if batt is removed from vehicle Then reinstalled?

    • Rae Castillon Says

      Hi Michael,

      The Passlock system is a security feature in GM vehicles, including the 1999 Silverado, designed to prevent unauthorized starting of the vehicle. While cutting wires in the Passlock system may bypass the security feature temporarily, it’s not a recommended or reliable long-term solution.

      Removing the battery from the vehicle and then reinstalling it may not necessarily reset the Passlock system. The Passlock system typically stores data in the vehicle’s computer that can persist even if the battery is disconnected. Additionally, some GM vehicles require a specific relearn procedure to reset the Passlock system after any tampering or disconnection of components.

      To reset the Passlock system properly, you should consider the following steps:

      Reconnect any Cut Wires: If you have cut wires as part of your temporary bypass, it’s advisable to reconnect them to their original state.

      Perform a Relearn Procedure: GM vehicles often require a relearn procedure to reset the Passlock system. This usually involves a series of key cycles and ignition sequences. The exact procedure can vary depending on the vehicle’s make and model. You can usually find the specific relearn procedure for your Silverado in the vehicle’s service manual or by consulting a GM dealership or qualified mechanic.

      Address the Root Issue: Instead of bypassing the Passlock system, it’s recommended to diagnose and address the root issue causing the Passlock problem. Common issues include faulty ignition switches, damaged wiring, or malfunctioning Passlock components. Addressing the underlying problem will provide a more reliable and secure solution.

      Consider Professional Assistance: If you’re not comfortable performing these procedures or troubleshooting the Passlock issue yourself, it’s a good idea to seek professional assistance. A certified mechanic or GM dealership can diagnose the problem accurately and perform the necessary repairs or relearn procedures.

      Keep in mind that tampering with the Passlock system or attempting to bypass it may lead to unintended consequences, including potential electrical or security issues. It’s always best to address the problem properly to ensure the safety and reliability of your vehicle.

  • Abraham Gregor Says

    I lost the keys to my 2014 Tahoe. So I parked it and somebody broke the driver side window. How do I start it with no key?

    • Rae Castillon Says

      Hi Abraham,

      I’m very sorry to hear about your situation. The first thing that you need to do is to contact the authority to report the incident about the broken window. Unfortunately, we can’t help you start the car without the key. But you may contact the dealership or a trusted key replacement company to replace the key for you.

  • Daniel lozano Says

    I have a passlock ll system in my 2008 gmc envoy, I read 33 ohms with my meter across the black and yellow wires (key on or off) If I install a 2.2k ohm resistor in series with the yellow wire will this start my gmc?

    • Rae Castillon Says

      Hi Daniel,

      Based on the information you’ve provided, it’s really difficult to determine definitively whether installing a 2.2k ohm resistor in series with the yellow wire will allow your GMC Envoy to start. But, I can offer some insights.

      The Passlock II system is an anti-theft feature in vehicles manufactured by General Motors, including the GMC Envoy. It’s designed to prevent unauthorized starting of the vehicle by disabling the fuel injectors if the proper key is not used.

      The resistance value you measured across the black and yellow wires indicates the resistance of the key pellet or the ignition lock cylinder’s resistor. This resistance is part of the security system’s authentication process.

      If you’re considering installing a 2.2k ohm resistor in series with the yellow wire, it’s likely an attempt to mimic the resistance value of the key pellet or ignition lock cylinder. However, without knowing the exact resistance value required by the Passlock II system for your specific vehicle, it’s challenging to confirm whether the 2.2k ohm resistor will work.

      Moreover, tampering with the vehicle’s security system can have unintended consequences and may not be legal in some jurisdictions. It’s essential to consult with a qualified automotive technician or contact the manufacturer for guidance on bypassing or repairing the Passlock II system in your GMC Envoy. They can provide you with accurate information and ensure that any modifications made to the vehicle are safe and legal.

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