2012-2020 Chevrolet Sonic: Solving Key, Fob, and Ignition Problems

Symptoms of Key and Ignition Failure

Problems with the Chevrolet Sonic's key and ignition system can leave you stranded. Understanding the specific symptoms can help you pinpoint the cause, which may not always be the key itself.

1. Key Gets Stuck in the Ignition

This is one of the most common complaints from Sonic owners. After parking and turning the engine off, the key refuses to turn to the final "off" position to be removed. In most cases, this is not a failure of the key or the ignition cylinder. The problem is usually a faulty component inside the automatic gear shifter assembly. A small switch that detects when the car is in Park fails, and the car's safety interlock prevents the key from being released. Wiggling the shifter or repeatedly pressing the shifter button may temporarily release it. Some owners report that the silver button on the shifter itself gets physically stuck, which also traps the key.

2. Key Won't Turn in the Ignition

If you can insert the key but it won't turn at all, or only turns part-way, there are a few likely causes. The simplest is a locked steering wheel; this happens if the wheel was moved after the car was shut off. Gently wiggling the steering wheel back and forth while trying to turn the key will usually free it. If that doesn't work, the issue could be a very worn-out key blade that no longer properly engages the tumblers, or a failed ignition lock cylinder.

3. Car Won't Start and Security Light is Flashing

If you turn the key and the engine cranks but won't start (or won't crank at all) and you see a flashing light on the dashboard shaped like a car with a lock, the vehicle's anti-theft system (immobilizer) is active. This means the car is not recognizing the transponder chip in your key. This can be caused by a weak battery in the key fob, a temporary glitch in the car's computer, or a failed component like the immobilizer transceiver ring around the ignition. Often, this can be fixed with a "10-minute relearn" procedure.

4. Remote Buttons (Lock/Unlock) Don't Work

The rubber membrane over the buttons on the flip-key fob is known to wear out, crack, and eventually fall apart. This can make the remote functions difficult or impossible to use. While the physical key and transponder chip may still work to start the car, you will lose the convenience of keyless entry. In other cases, the issue could be a simple dead CR2032 battery inside the fob.

5. Vehicle Tries to Start on Its Own

A strange and concerning issue involves the vehicle powering up, cranking, or even starting on its own when the key is inserted or left in the ignition. This is often accompanied by the "key in" warning chime not working. General Motors issued a Technical Service Bulletin (TSB PI1329) for this problem, identifying the cause as a worn ignition cylinder actuator. The wear causes incorrect voltage signals to be sent to the Body Control Module (BCM), which misinterprets it as a command to start.

Known Issues, TSBs, and Recalls

Several official documents relate to the Sonic's ignition and security systems.

• TSB PI1329: Addresses vehicles that may power up or attempt to start on their own due to a worn ignition cylinder actuator. The recommended fix is to replace the ignition lock cylinder (Part No. 20766607).
• Recalls for Inoperative Warning Chimes (e.g., 16V422000, 16V257000): Multiple recalls were issued because a software issue in the radio could cause all warning chimes to fail. This includes the chime that alerts the driver if the key is left in the ignition, which is a violation of federal safety standards.
• Shifter Interlock Failure: While not a formal recall, the issue of the key getting stuck due to a failed park-detect switch in the shifter is a widely documented problem in owner forums.

Buying a Used Vehicle Key Set

Purchasing a used key set can be a cost-effective solution, but it requires careful attention to detail. A "key set" can refer to just the key/fob, or a complete package including the ignition lock cylinder and sometimes the door and trunk lock cylinders from a single donor vehicle.

What to Inspect on a Used Part:

• Key Fob Casing: Check the rubber buttons for cracks or excessive wear. Ensure the flip-key mechanism operates smoothly and the case is not cracked.
• Key Blade: If you are buying just a fob with plans to swap your old key blade, inspect the small roll pin area for damage. If you are buying a full set with a key, check the blade for excessive wear or damage.
• Lock Cylinders (if included): If buying a full set, ensure the key turns smoothly in the ignition and door lock cylinders.

Compatibility is Crucial:

• Match the FCC ID and Part Number: The most important step is to match the FCC ID (e.g., OHT01060512 or KR55WK50073) and the part number on the back of your original fob.
• Button Configuration: Ensure the used fob has the same number of buttons (3, 4, or 5) for the same functions (lock, unlock, trunk/hatch, remote start, panic) as your original.
• Full Lock Set: Buying a complete set (all locks and the matching key) from a single vehicle is a great option if you've lost all your keys or have multiple damaged locks. This way, one key works for everything without needing a locksmith to re-key the cylinders. However, the key's transponder will still need to be programmed to your car.

Why Used OEM is a Smart Choice:

Used OEM (Original Equipment Manufacturer) key fobs contain the original, high-quality electronics. Many cheap aftermarket fobs have weaker signal strength and a higher failure rate. With a used OEM fob, you are getting a part that was built to last, often just in a new plastic case. Swapping the internal board from a used OEM fob into your existing key (if only the case is broken) or having it programmed to your car is often more reliable than trusting a new, unproven aftermarket part.

Replacement and Programming

Replacing a key or ignition cylinder for the Sonic involves both mechanical and electronic steps.

Programming a New Key

If you have at least one working, recognized key, you can typically program additional keys yourself without special tools.

1. Insert the original, working key into the ignition and turn it to the ON/RUN position (where the dash lights come on).
2. Turn the key back to OFF and remove it.
3. Within 5 seconds, insert the new, cut key and turn it to the ON/RUN position.
4. The security light on the dash should turn off after a few seconds, indicating the new key has been programmed.
5. Test the remote buttons and try to start the car with the new key.

If you have lost all your keys, you cannot perform this procedure. You will need an automotive locksmith or a dealership to program a new key to the car using a diagnostic scan tool.

Ignition Lock Cylinder Replacement

If the ignition lock cylinder itself has failed, it must be replaced. You can buy an "uncoded" OEM cylinder, which a locksmith can then assemble with new tumblers to match your existing key. This avoids needing separate keys for the ignition and doors.

Cost Comparison

Frequently Asked Questions (FAQ)