What Is the P0599 Code?
Symptoms
Causes
Seriousness
Can I Still Drive?
Diagnose
Difficulty of Inspecting
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The definition of code P0599 is “Thermostat Heater Control Circuit High.” This code means the system that electronically controls your engine thermostat has malfunctioned, sending your powertrain control module (PCM) or engine control module (ECM) a control voltage reading that is too high. As a generic powertrain code, you might see this code in any OBD-II vehicle equipped with an electronically controlled thermostat.
More About Error Code P0599
The electronically controlled thermostat is a special system that controls coolant flow or engine temperature electronically rather than mechanically, as many vehicles do. This increases fuel economy and reduces emissions in exchange for sometimes reduced power. In the United States, it’s less common to see this kind of electronic thermostat system, but many German-manufactured vehicles, including BMW, Mercedes, Audi, Volkswagen, and Jaguar, will use this system. If you’re seeing this diagnostic trouble code, it means that the control voltage, which tests whether the system is functioning properly, has returned with excessive voltage, potentially indicating a problem with function or communication.
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What Are the Symptoms of a P0599 Code?
Most of the time, there won’t be any noticeable symptoms of the P0599 generic code outside the check engine light. Notably, this code doesn’t mean there is a problem with the electronically controlled thermostat but that a control voltage has returned incorrectly. This can, of course, result in issues with maintaining the correct temperature. But the code doesn’t indicate anything about your vehicle’s optimal temperature. Occasionally, you may see the temperature gauge stop responding, which will likely fail in either an abnormally high or abnormally low-temperature reading. Outside of this, you likely won’t notice any operational issues.
What Are Some Causes of a P0599 Code?
Usually, this diagnostic fault code involves either a fault within the electrically operated thermostat or a problem with an electrical connector or other wiring, such as the wiring harness between the onboard computer and the thermostat. Occasionally, this code may also be a secondary problem from another code, such as a problem with a coolant leak. Finally, if there is no other option, the problem might be within your vehicle’s engine management computer, usually called the Motronic, but this is unlikely.
How Serious Is the P0599 Code?
The P0599 code isn’t urgent, but it should be treated with the same seriousness as you treat most engine codes. Although it won’t result in immediate engine damage, it can cause damage over time. This is because if your vehicle cannot read the engine temperature in an electronically controlled thermostat vehicle, it can cause the PCM or ECM to stop controlling the temperature as accurately. In general, you should recognize this code as important to fix but not so severe that you must pull your car over immediately.
Can I Still Drive with a P0599 Code?
You will still be able to drive with the P0599 code, as it rarely results in any major drivability issues. However, it’s good to remember that you should avoid driving with this code, even if it’s physically possible. Whenever you’re dealing with an engine code, it’s always best to stop driving and get help. You never know what this code might do to your engine, so if you can stop and fix the problem early on instead of waiting until it spirals into a real problem, it’s best to do so.
How Easy Is It to Diagnose a P0599 Code?
The P0599 code can sometimes be difficult to diagnose because it can be difficult to diagnose an electronically controlled thermostat system if you’ve never looked into one before. Because these problems are fairly uncommon, finding resources to inform you about them can also be difficult. If you’re ever uncertain whether you can effectively diagnose the P0599 code, you should talk to a certified mechanic for professional help.
How Difficult Is It to Inspect a P0599 Code?
The inspection process of the P0599 code can be just as difficult as the diagnostic process and sometimes even more difficult. This is partially because the core problem is often a wiring problem, which means you’ll probably need to do a visual inspection of the wiring so you can find the core issue. If there is an easily apparent issue, a visual inspection may be fairly easy, but if the problem is less obvious, this can be extremely difficult, especially without wiring diagrams and a vehicle service manual. If you’re looking for help, a professional mechanic can help you inspect this code without making any common mistakes.
Need Additional Help with Your P0599 Code?
Many people need additional help with their P0599 error code. If you’re looking for that help, there are plenty of places to get it.
First, you should find an auto repair shop in your area. Make sure you indicate your car type when you first contact the shop. While most repair shops will be able to handle all kinds of cars, these systems are in vehicles that are fairly uncommon in the United States, so it’s best to let the shop know that upfront.
Additionally, sometimes this code comes with additional codes on your code scanner. The OBD-II database at KBB.com will give you more insight into these codes, so you can fix all the problems you’re experiencing, not just some.
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