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P0508 OBD-II Trouble Code: Idle Air Control System Circuit Low

Check Engine Light

P0508 code definition

When this code appears and is stored in the onboard computer, it means that the idle air control system circuit is low.

What the P0508 code means

The P0508 code means that the powertrain control module has sensed that there is some type of inconsistency in the engine idles RPM. Whenever the PCM discovers that the engine is idling too high or too low, it will try to correct the RPM. If they can’t, it will store the code.

What causes the P0508 code?

The following are some of the most common causes of the P0508 code.

  • The Idle Air Control, or IAC, motor harness could be shorted or it could be open
  • The IAC can also have a bad electrical connection due to the motor circuit
  • The IAC itself could be faulty
  • Dirty throttle body bore

What are the symptoms of the P0508 code?

Those who have the P0508 code in their vehicle may find that the engine idle RPM is low or high. The engine might stall when at low speeds, and when the accelerator is not depressed. In addition, the engine may sometimes stall when releasing the throttle. Additionally, a malfunction indicator light will likely illuminate.

How does a mechanic diagnose the P0508 code?

One mechanic is trying to diagnose the P0508 code, he or she will connect and OBD-II scanner to the vehicle’s onboard computer. They will then check to see what codes are stored and they will reset them. At that point, they will run the vehicle to see if the code returns. If the P0508 trouble code does return, they will then begin looking at the potential causes, such as the IAC.

Common mistakes when diagnosing the P0508 code

One of the mistakes made when diagnosing the P0508 code is immediately assuming that the issue is with the IAC components. In some cases, cleaning the throttle body bore first can help to clear up the problem.

How serious is the P0508 code?

No one likes to have a vehicle that doesn’t run properly, and the P0508 code means that they engine idle RPM is not performing well. As mentioned, this could mean the engine will stall at low speeds and when the accelerator is not pressed, such as well waiting at a stoplight or even taking a turn. This can cause some serious problems will driving, and it has the potential to be dangerous. It is important to take care of this code as soon as possible to ensure proper performance of the vehicle. Those who do not take care of this and other codes may find that their vehicle develops other problems as well.

What repairs can fix the P0508 code?

The following are some of the repairs and methods used to fix the P0508 code.

  • First, they will check to determine whether the P0508 code has been set by mistake
  • If code is legitimate they will want to check the throttle body bore and clean, and then reset and check the code
  • They will then want to check the electrical connections and circuits with the IAC to make sure they are in proper working order, and will make replacements for repairs to those connections as needed
  • In some cases, they may need to replace the IAC
  • They may need to replace the PCM, but this is extremely rare

Additional comments for consideration regarding the P0508 code

When the P0508 code appears, it is generally noticed by the driver. Even though the vehicle may still drive, there will be enough problems with the idling that it will need repair. Do not wait to get this issue examined and then repaired by a qualified and certified mechanic. Deal with the issues as they appear to ensure the vehicle stays in good working order.

Need help with a P0508 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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