P0519 OBD-II Trouble Code: Idle Air Control System Performance
Diagnostic Trouble Code (DTC): P0519
P0519 code definition
The P0519 trouble code is defined as idle air control system performance.
What the P0519 code means
When a vehicle idles, it still maintains a certain predetermined RPM decided on by the manufacturer. The PCM (Powertrain Control Module) monitors this RPM to ensure it is at the correct level. There is an acceptable range and if the RPM goes above or below it, the PCM will respond by trying to fix it. If it is unable to do so, the P0519 code will be stored.
What causes the P0519 code?
The most common reason for the P0519 code, by far, is the throttle body being carbon coked at the bore. If that is not it, the cause could be:
- Open or shorted electrical circuits
- A sizeable vacuum leak
- A broken idle air control valve
Though it’s rare, if none of the above is responsible for the code, then the PCM could be the problem.
What are the symptoms of the P0519 code?
If the P0519 code has been stored by the vehicle’s PCM, the RPMs should show running high or low when idling; that is literally the thing that causes this code. The Check Engine Light should come on too.
However, the engine may also stall out when driving low speeds and the accelerator isn’t being depressed. The engine may also stall intermittently when the throttle is released.
How does a mechanic diagnose the P0519 code?
The first thing a mechanic will do is use an OBD-II scanner to retrieve all the trouble codes that have been stored by the PCM. Once they know about the P0519 code, they should inspect the connectors and wiring that work with the air control system.
If that doesn’t help, the problem is probably an intermittent one which can be a lot harder to properly diagnose. Ideally, the mechanic may have to use a specific scanner program that will take them through the IAC system test necessary to proceed with the diagnosis.
Otherwise, the mechanic may simply have to let the problem get worse before they do another inspection to find the source of the problem.
Common mistakes when diagnosing the P0519 code
One common mistake a lot of mechanics make once they know a P0519 code has been stored is immediately replacing the idle air control part. What they should do is clean off the throttle body bore first. Otherwise, there’s a good chance of a misdiagnosis occurring.
How serious is the P0519 code?
Even if it just seems like a small problem at first, it won’t be long before the P0519 problem begins making it difficult to drive. It’s not necessarily a dangerous problem, but the engine can suddenly idle while on the road. This will continue to happen until repairs are done.
Furthermore, as we touched on above, this problem can grow into something much worse if it isn’t caught early and properly diagnosed.
What repairs can fix the P0519 code?
A lot of the time, all it takes is simply cleaning off the throttle bore body or the wiring and connectors the air control system needs to work properly. As we mentioned above, the most common reason for the code being triggered is the throttle body being carbon coked, so the “repair” may call for nothing more than a thorough cleaning of this component.
Other times, it could be that there is a large vacuum leak, which will most likely call for a replacement. If the idle air control valve is broken, that will either need to be repaired or replaced.
Additional comments for consideration regarding the P0519 code
Unfortunately, if there’s no clear source for the problem, and the PCM has been checked to make sure it is working correctly, the driver will simply need to put up with the issue a while longer until the cause makes itself known.
Need help with a P0519 code?
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