What Codes Will This Page Cover?
On this page, you’ll learn more about the following codes:
- P0508 Idle Air Control System Circuit Low
- P0509 Idle Air Control System Circuit High
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What Is the P0508 Code?
Symptoms
Causes
Seriousness
Can I Still Drive?
Diagnose
Difficulty of Inspecting
Get Additional Help
The code definitions for codes P0508 and P0509 are “Idle Air Control System Circuit Low” and “Idle Air Control System Circuit High,” respectively. These codes indicate that your powertrain control module (PCM) or engine control module (ECM) has identified an issue with the voltage for the circuit related to the Idle Air Control system, being either too high or too low to meet manufacturers’ standards. As generic powertrain codes, you may find codes P0508 and P0509 picked up by an OBD-Il scanner in many vehicles.
More About the P0508 Code
Your idle air control system (IAC system) helps your vehicle idle with the throttle plate closed. When your vehicle stops, the throttle body allows very little air to enter the engine, but if no air were to enter the engine, it would stall. The IAC system has a passage to bypass the throttle plate, allowing the ECM to adjust idle speed and decelerate when the throttle is not applied. The PCM uses information from your throttle position sensors, oxygen sensors, crankshaft position sensors, and more to determine how much air can enter the intake manifold and improve engine performance. These error codes indicate that the circuit used to send control information to the IAC system is returning an incorrect reference voltage.
What Are the Symptoms of a P0508 Code?
Issues with diagnostic trouble codes P0508 and P0509 can end up resulting in a variety of issues with your engine’s ability to run smoothly. The most common symptoms include your engine idle speed being at a very high engine RPM, your engine stalling while idling, general rough idle even at normal engine load, and unusual noises coming from the throttle body. It’s also very common to see additional IAC-related codes when you see these codes. The check engine light should also turn on when codes P0508 and P0509 pop up.
What Are Some Causes of a P0508 Code?
There are a number of different causes that could relate to the P0508 and P0509 trouble codes. Here are a few of the most common P0508 and P0509 causes:
- Malfunctioning IAC motor or IAC valve
- Engine vacuum leaks
- Electric connection issues, such as open connectors or faulty wiring
- Carbon buildup in the throttle body or IAC valve
- General issues with the PCM, although this is uncommon
This is not a complete list of possible causes of the P0508 and P0509 codes, so your specific issue may not even appear on this list.
How Serious Is the P0508 Code?
The P0508 and P0509 engine codes are extremely serious. This circuit allows your vehicle to continue idling correctly; if you have an issue with your vehicle’s idle, you could end up not being able to drive at all because your car could start idling at any stop light or even before you pull the car out of the driveway. Even if you currently don’t see any drivability issues, it’s still extremely important to get help as soon as possible, as these symptoms can turn up at any time.
Can I Still Drive with a P0508 Code?
You can sometimes still drive with the P0508 and P0509 codes active. However, as already mentioned, it’s not generally considered a good idea. This is because, while these codes don’t usually result in a no-crank or no-start condition, they can cause your vehicle to stall out at idle, which can occur when stopping at a stoplight or starting your car. Plus, fuel efficiency often suffers.
How Easy Is It to Diagnose a P0508 Code?
Vehicle diagnostic processes for codes P0508 and P0509 can be difficult. In many cases, these codes come bundled with related idle air control circuit trouble codes or trouble codes generally related to the idle air control system. While there are some common causes for these codes, there are a wide variety of possible causes, especially if there’s an underlying cause to multiple codes. It’s likely that you’ll need to do a lot of work to diagnose codes P0508 and P0509, which is one reason it could be a great choice to trust an expert.
How Difficult Is It to Inspect a P0508 Code?
It’s often somewhat difficult to inspect the P0508 and P0509 codes. It can be important to have a vehicle information source like a repair manual, wiring diagram, and technical service bulletins, and you may need a variety of tools, ranging from repair manuals to smoke vacuums for diagnosing engine leaks and more, all allowing you to inspect this code. This is one of the reasons it’s common to get help from an expert instead of trying to DIY this fix.
Need Additional Help with Your P0508 Code?
Many people end up needing extra help with the P0508 and P0509 codes. If you’ve decided that expert assistance for repair steps is the right choice, here’s how you can get that help.
To start, you’ll want to find an auto repair shop in your area. Finding a local auto repair shop is a great starting point, especially because these codes can make your vehicle difficult to drive safely.
You may also want to check out the OBD-Il database at KBB.com. This database can give you more insight into additional codes on your diagnostic scanner, which is a common problem with the P0508 and P0509 codes.
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