P0633 Code — Immobilizer Key Issues? Today’s cars are fitted with numerous security features that prevent theft. Unfortunately, the windows and door locks aren’t enough to prevent a vehicle from being stolen, which is why additional security features are used. Aside from aftermarket alarms and steering wheel locks, one of the standard security features on almost any car manufactured today is the immobilizer system. One way of knowing you have an immobilizer key issue is when the P0633 check engine light code is stored in the car’s ECU. In this article, we’ll talk about the causes, common symptoms, and how to properly diagnose and fix the P0633 code on your own if possible. What is the P0633 Code, and What Does It Mean? The P0633 fault code isn’t a common one, but when it appears, it means that the car’s ECU is unable to recognize the immobilizer key. In other words, it thinks that the wrong key is being used to start the car, or the key isn’t programmed. As a result, the car’s security system will prevent the engine from starting. What Is a key immobilizer, and What Does It Do? A key immobilizer is a crucial safety feature found in almost all modern vehicles. It’s a small electronic device that allows the linked key or key fob to turn the car’s engine on. This is possible by using small microchips and a matching transponder found in the key. The key immobilizer prevents the engine from starting unless a key with a corresponding transponder is used. When a key or key fob with a matching transponder is inserted in the ignition, the transponder sends a specific coded signal to the receiver which tells the ECU that the correct key is being used. This system is made to prevent theft. What Can Cause a P0633 Code? Thankfully, the P0633 code is triggered only due to a number of certain causes, which are all related to the immobilizer key or related parts. The most common causes for a P0633 code include a weak immobilizer key battery, an immobilizer key fault, a defective ignition cylinder, faulty wiring, and a dead battery that reset the ECU’s programming. What Are the Common Symptoms of P0633 Fault Code? The P0633 fault code doesn’t show many symptoms, but those that are noticeable clearly indicate an issue with the immobilizer system. These symptoms include the inability to start the engine, the P0633 fault code stored in the ECU, and issues with locking and unlocking. Unfortunately, these symptoms come without a warning. This means that your car will work perfectly one day, and show one or more of these symptoms the other. If your car is fitted with a mechanical lock, you’ll likely be able to unlock it, but it’s possible for other safety features such as the alarm to go off.
The P0633 code is considered a serious one because it can leave you without the possibility of starting your car at any time. This is why it’s of the essence to address any and all symptoms accordingly as soon as they appear. How to Diagnose and Fix the Cause of P0633 Code Diagnosing and fixing any fault code starts with checking the ECU with an OBDII scanner. This is a crucial part of the process because there might be an underlying issue that may cause similar symptoms to those caused by the P0633 code. If there are no more codes stored in the ECU aside from the P0633 code, the next step is finding what is the intermittent cause. There are a few common causes that trigger the P0633 code, one of which is faulty wiring. Visually inspect the wiring and fuses first, and if there are visible cracks or corrosion, the wires and connectors should be replaced to fix the issue. You should start with this because faulty wiring can cause much bigger damage to the car than just an issue with starting your car. Once the wiring is sorted, reset the fault code using your OBDII scanner, and try starting your car. If the wiring was causing the issue, everything should work fine.
If wiring isn’t the issue, the second step is to check the car’s battery and the battery in the immobilizer key. The car’s battery should be tested with a voltmeter, while the immobilizer key battery needs to be replaced with a new one. If the car battery is old, or weak, you’ll need to replace it with a new one. In some car models, this will also require additional immobilizer coding. The same applies to replacing the battery in the immobilizer key. Some cars have a simple procedure to program the immobilizer to the ECU, however, specific cars require specialized tools for the job. Before trying to fix the P0633 code by yourself, check the owner’s manual on how to program the immobilizer key. Lastly, you should check the ignition cylinder because in some cases, it can lead to the P0633 code being triggered.
Does P0633 Clear Itself? The short answer is – YES. The P0633 code will clear itself once the immobilizer allows the car to start. Once the ECU recognizes the correct signal from the immobilizer key, it should allow the engine to start, and once it does, the fault code should be automatically cleared from the ECU. The only reason why the P0633 code won’t clear itself is if the cause for the code itself is a faulty ECU. This is highly unlikely because a faulty ECU will usually show other symptoms or show other fault codes. Can You Drive with a Bad Key Immobilizer? A bad key immobilizer won’t allow the driver to start the car’s engine, so to answer this question, it’s sufficient just to say NO. The scenario where the key immobilizer goes bad in the middle of driving is highly unlikely, and even if the car’s battery dies during driving, you’ll still be able to drive the car until the engine stops. Once it does, you won’t be able to start it again until the issue is resolved. If you manage to start your car after one or more symptoms of the P0633 code appear, it’s recommended that the only route you take is to the mechanic who will diagnose and fix the issue. If you’re experienced in working with various vehicle systems, you can try to diagnose the issue yourself. Driving for any other reason isn’t recommended. Use Only the Highest-Quality Replacement Parts The immobilizer system doesn’t require regular maintenance, but it’s a matter of time before the P0633 code will show itself for one reason or another. Whatever the reason for the P0633 code is, it’s essential to use the highest-quality replacement parts to keep the immobilizer system functioning properly for a longer period of time. Whether it’s an ignition cylinder or a battery that’s causing the issue, make sure to follow manufacturer recommendations and use genuine, or OEM parts as a replacement. At eEuroparts.com, find a wide range of replacement parts for most European cars available in the US, and ordering is as simple as it gets. By selecting the year, make, and model of your car, you’ll get a list of compatible replacement parts from some of the top brands in the industry.
