What Is the P0638 Code?
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The P0638 generic trouble code indicates that the powertrain control module (PCM) or engine control module (ECM) has identified some kind of problem with the throttle actuator control range, specifically in Bank one. This exact code definition refers to a generic powertrain code that can show up in many OBD-II-enabled vehicles. However, it only occurs in an engine with electronic throttle control, usually in newer vehicles. While this generic OBD-II powertrain code indicates that it is a problem in Bank one, there is usually only one throttle body in the vehicle. This means that it often refers to your main throttle body.
More About Error Code P0638
The P0638 diagnostic trouble code concerns your electronic throttle control (ETC). The ETC controls the amount of air entering the intake system — it’s a butterfly-style flap that varies the opening to allow more or less air flow into the intake. Too much air will produce a lean fuel-air mixture, while too much fuel will produce a rich mixture. The throttle actuator is a more modern version of the throttle body, historically controlled by physical cables. If the throttle actuator is in the wrong position, which may be due to a problem with the control circuit or the actual throttle valve, the vehicle will log a P0638 code to identify this problem.
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What Are the Symptoms of a P0638 Code?
Symptoms of code P0630 will depend on various components, including how severe the code issue is, what the actual problem is, and whether any other codes are happening alongside code P0638. You should expect to see the check engine light turn on, and you will likely also see varied engine performance problems, like rough running and stalling. In some situations, the vehicle will be stuck in Limp Mode, also called Limp Home Mode, which may reduce vehicle speed and shut off certain systems like your air conditioning system.
What Are Some Causes of a P0638 Code?
A faulty throttle body assembly or bad throttle position sensor are the most common causes of the P0638 code. Most of the time, this code occurs because there’s a problem with the sensor or the throttle actuator, so it’s best to check those first. A clogged throttle body or dirty throttle body can also cause loss of throttle control and other throttle actuator malfunctions. In some situations, it may have to do with electrical wiring problems, and in very rare cases, you may be dealing with a PCM malfunction, although this is uncommon and should be the last thing you consider.
How Serious Is the P0638 Code?
The P0638 code is very serious. The throttle body is one of the core components of your vehicle, as it has to do with how much fuel the injectors are spraying into your engine. The most common issue is that the vehicle can’t accelerate correctly, which means most vehicles will go into “Limp Mode” or “Limp Home Mode,” allowing only very limited acceleration so that the driver can safely park. In some cases, you risk severe fuel mismanagement within the engine, resulting in misfiring, stalling, and even a vehicle that doesn’t start or turns off when idle. Complete failure can also result in extensive damage. Always tackle this problem as soon as possible.
Can I Still Drive with a P0638 Code?
In some cases, you may not physically be able to drive if the P0638 code is active. The P0638 code will occasionally allow you to drive, albeit often with engine performance issues, but you should avoid doing so. You may be wasting fuel and putting your vehicle at a higher risk of severe complications if you continue to drive with the P0638 code active. If you know this code is active, stop driving and get help with the problem.
How Easy Is It to Diagnose a P0638 Code?
The diagnosis process for the P0638 code often isn’t that difficult. Most of the time, this problem has to do with the throttle actuator or the throttle position sensors, and in almost every case, this code means that you need to replace the broken part. Plus, while generic steps can help, a non-professional mechanic likely won’t know the exact steps important for your vehicle’s make and model. That’s often the difficult part for DIYers. If you don’t have the information necessary to replace the parts, it doesn’t always matter if you can diagnose the code.
How Difficult Is It to Inspect a P0638 Code?
The inspection process for OBD code P0638 can be more difficult than diagnosis, as you might need specialty tools to inspect the throttle actuator and ensure you know how to fix it. You may also need to know how to do a quick test drive and a complete drive cycle, as a couple of drive cycles may be necessary to see whether the error code returns after clearing it. If you want to inspect the P0638 error code and don’t have much experience handling throttle actuator issues, take the code to a professional mechanic instead of trying to do it yourself. This will also prevent a returning code after repairs, as a professional mechanic can check the entire throttle body and check for problems like an erratic throttle response.
Need Additional Help with Your P0638 Code?
Most people will need a professional diagnosis to help with fault code diagnosis for the P0638 code. Despite it not being exceptionally difficult to tell where the problem likely is, replacing a throttle body is not easy for most people.
If you need help with the P0638 generic code, you should find an auto repair shop in your area. Finding a local automobile repair shop will make getting your vehicle in for a fix easier.
This code can also come along with other fault codes that play a role in diagnosing and fixing the problem. The OBD-II database from KBB.com will help you understand these other codes to determine what’s happening with the information from a generic code reader.
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