How To Permanently Disable A GM PassLock System Step-by-Step

If your GM vehicle’s PassLock system is preventing your car from starting, you may need to figure out how to permanently disable and bypass it. PassLock is an anti-theft feature designed to prevent unauthorized engine starts. However, over time, the system could malfunction due to wiring issues, weak batteries, or sensor failures. Thus, leaving you stranded.

Thankfully, trying to permanently disable the PassLock system in vehicles is really easy, whether you have PassLock 1, 2, or 3. However, before you resort to a full bypass, it can be worth attempting a simple PassLock relearn procedure, which might be able to reset minor glitches and get your car running again. Below, we’ll walk you through the relearn procedure.

Beyond that, if a relearn doesn’t work, further below, we’ll also guide you each step of the way with performing a resistor bypass method to permanently disable your GM PassLock system. And, we’ll also look at wiring modifications needed to override the system. So, following along if you want to learn how to regain control over your car’s ignition system!

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

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…

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 Bypass GM PassLock System (Step-by-Step)

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:

PassLock 1 vs PassLock 2 vs PassLock 3

For those of you who are interested, as we noted earlier, there are 3 versions of GM’s PassLock system. There’s PassLock 1, 2, and the newer 3. So, before you begin bypassing your GM vehicle’s PassLock system, it’s important to understand which version of PassLock your car has. After all, they each have different security mechanisms and varying points of failure.

As such, we’ve prepared this handy little table below to showcase the differences between PassLock 1, PassLock 2, and PassLock 3:

PassLock Version	Model Years	Technology Used	Common Failures	Bypass Difficulty
PassLock 1	1995–2002	Resistor pellet in key, and Theft Deterrent Module (TDM)	Worn key, dirty ignition contacts, as well as a failed TDM	Moderate (Requires resistor matching)
PassLock 2	1995–2008	A hall-effect sensor in the ignition, and TDM	Faulty sensor, weak battery, as well as loose wiring	Easy (Cut & rewire yellow data wire)
PassLock 3	2003+	Transponder key, and Immobilizer control module (ICM)	Dead key fob, failed ICM, in addition to BCM issues	Hard (Requires key programming or module replacement)

Hopefully, that table should quickly help you identify exactly what version of GM PassLock you have:

• If your GM vehicle was built before 2002, it likely uses PassLock 1. It has a resistor pellet in the key.
• Vehicles built between 1995 and 2008 mostly have PassLock 2. They rely on a Hall-effect sensor.
• Otherwise, vehicles made from 2003 onward use PassLock 3. It’s way more advanced and incorporates a transponder chip in the key

GM PassLock Troubleshooting

Whether you don’t want to permanently disable the GM PassLock system or don’t want to resort to the nuclear option, there are other troubleshooting steps that you could consider besides trying to relearn the anti-theft system. Here are some other fixes and troubleshooting techniques that you ought to bear in mind:

1. Replace the PassLock Sensor

GM’s PassLock system relies on a Hall Effect sensor inside your car’s ignition switch to detect key rotations. Over time, this sensor could unfortunately fail due to wear, corrosion, or electrical faults. As a result, this causes the system to falsely detect an unauthorized key. Here are some early symptoms and signs of failure to keep an eye out for:

• Your car’s security light stays on or flashes when it’s trying to start.
• The engine cranks but it won’t properly start.
• Your car randomly shuts off while driving (in rare cases).

Now, with that in mind, here’s how you can go about fixing this:

• PassLock 1 and 2 – The aforementioned Hall Effect sensor is built into your car’s ignition switch. So, replacing the switch assembly is required to fix it.
• PassLock 3 – This newer system uses a transponder chip inside the key. Therefore, a failing key chip may require a replacement key or reprogramming at a dealership.

NOTE: If you’re replacing the sensor, make sure that you perform a PassLock relearn procedure afterward. This would help the new sensor to sync properly with the system.

When it comes to how much it’ll cost you to fix this, here’s the damage:

• DIY ignition switch replacement: $50–$150
• Professional repair: $300–$500
• New key & reprogramming: $50–$200

2. Check for Wiring Issues

Since the GM PassLock system relies on signals between the ignition switch, BCM, and PCM, faulty wiring can disrupt communication and prevent the car from starting. This is a rather common issue, especially in some of your older GM vehicles. Early warning signs and symptoms of failure include:

• Your car’s security light flickers or continues to stay on.
• Your car won’t start intermittently (this is especially so in colder weather).
• Moving the steering column or wiggling the key temporarily fixes the issue.

Now, before you even attempt to fix it, here are some things that you need to closely check and inspect:

• Yellow PassLock wire – This is a common point of failure in some GM vehicles.
• Ground connections – A loose ground wire can cause electrical noise, triggering the PassLock system.
• BCM connectors – You have to make sure that all plugs are secure and corrosion-free.

If you’re keen on fixing this yourself instead of opting for a professional repair, here’s an overview of what needs to be done:

• You could try reconnecting loose wires to ensure a snug fit in connectors.
• Elsewhere, you could also try cleaning any corrosion using an electrical contact cleaner.
• Alternatively, try to repair broken wires by soldering or using heat-shrink tubing.

Doing a DIY repair like this could save you a fortune. At most, you’d spend $30 on tools and supplies. On the other hand, a professional repair would set you back between $100 to $300.

3. Replace the BCM (Body Control Module)

Your car’s Body Control Module (BCM) is the ‘brain’ of your PassLock system. It processes signals from the ignition switch and determines whether or not to allow the engine to start. Now, if the BCM malfunctions, it can mistakenly activate PassLock, preventing your car from starting. Here are some signs of a faulty Body Control Module:

• Your car’s security light flashes on and off, even with a working key.
• Your car starts and then stalls immediately.
• Other electrical issues occur, such as power locks, windows, or interior lights malfunctioning.

To fix this, here’s what needs to be done:

• You can try using an OBD-II scanner to check for trouble codes (e.g., B2960, B2955, or B3031 related to PassLock).
• If your car’s BCM is faulty, then you’d have to replace it with a new or refurbished unit.
• But, make sure that the new BCM must be programmed for your vehicle, which can be done at a dealership or with specialized tools.

Be wary, though, if you replace the BCM (Body Control Module), a PassLock relearn procedure is required to sync it with your key and ignition system. Regardless, replacing your car’s BCM isn’t cheap:

• Used BCM: $100–$250
• New BCM + programming: $400–$800
• Dealer reprogramming fee: $50–$150