P0509 OBD-II Trouble Code: Idle Air Control System Circuit High

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE P0509 DIAGNOSTIC Get a fair and transparent estimate upfront
Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0509 code

P0509 is a diagnostic trouble code (DTC) for "Idle Air Control System Circuit High". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $79.99. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$79.99$20.00
Toyota$79.99$20.00
BMW$79.99$20.00
SCHEDULE P0509 DIAGNOSTIC Get a fair and transparent estimate upfront

check engine light

P0509 code definition

If this code is stored, it means that your vehicle’s PCM has picked up on an inconsistency regarding the RPM of the engine when it’s in idle.

What the P0509 code means

Every vehicle has a set RPM level it’s supposed to be at when in idle as predetermined by the manufacturer. Your vehicle’s PCM is in charge of monitoring the idle RPM to make sure it lands within a certain range. If it finds that it’s idling too high or too low, your PCM’s first response will be to restore an acceptable RPM on its own. However, if it is unable to do so, the P0509 code gets stored. Usually, the Check Engine Light will come on too.

What causes the P0509 code?

There are a few reasons that your vehicle’s PCM may store this code. By far the most common, though, is just that the throttle body bore is being choked by carbon coke. Other culprits you should know about are: * A sizable vacuum leak * A defective idle air control valve * Electrical circuits that are open or shorted Although it’s extremely rare, there’s also a chance that your stored P0509 code could be caused by a bad PCM.

What are the symptoms of the P0509 code?

Obviously, given the nature of this code, you’ll most likely notice that your engine’s idle RPM is much higher or lower than it should be. The former will probably be the more noticeable of the two symptoms because of the loud noise your engine will be making despite having very little demanded of it.

Another extremely obvious clue that something is wrong when a P0509 code has been stored is that your engine will stall out at very low speeds. This will occur even though your accelerator pedal isn’t even pressed down.

Furthermore, when you release the pedal, you may find that it stalls intermittently. Basically, once your vehicle’s RPMs stop performing normally when in idle, you can expect that it becomes much more difficult to drive or slow down as well.

How does a mechanic diagnose the P0509 code?

To diagnose the problem, your mechanic will need an OBD-II Scanner. This will allow them to draw out the P0509 code and any others your PCM has stored. After the mechanic understands all that they’re up against, they’ll continue by inspecting all the connectors and wires that may be involved.

If that doesn’t cure the issue, your mechanic will most likely look in on the fuses for any problems. However, usually, those first two steps are enough for a successful diagnosis.

Common mistakes when diagnosing the P0509 code

The most common misdiagnosis that involves this code is probably when idle air control components get replaced before the throttle body bore is even addressed. Doing this can lead to unnecessary expenses and/or not eliminating the actual problem.

How serious is the P0509 code?

This code isn’t serious insofar as it won’t put your life at risk. In fact, you’ll have a hard time getting your car to even move in many cases. Instead, this is a code that represents an extreme inconvenience. It should be fixed ASAP so you don’t end up stalling out when you’re driving.

What repairs can fix the P0509 code?

The most common repairs for curing your vehicle of P0509 involve addressing problems with the electrical components involved with deciding how many RPMs are appropriate. Another common solution would be cleaning out the throttle body bore. Far rarer would be having to replace a defective PCM.

Additional comments for consideration regarding the P0509 code

A digital ohmmeter can be a very helpful tool for this problem because you can use it to measure circuit resistance.

Need help with a P0509 code?

Do you need help with P0509? Then just complete this online form to set up an appointment with YourMechanic and receive a free quote. You can also call 1-800-701-6230 to speak with one of our service advisors. Simply let us know where you’d like us to send a certified mobile mechanic and they’ll perform all necessary repairs onsite.

trouble codes
Check Engine Light
P0509

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE P0509 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

4,255

Rating Summary
3,898
174
45
26
112
3,898
174
45
26
112
Ben

Ben

39 years of experience
1020 reviews
Ben
39 years of experience
Lexus LS430 - Check Engine Light is on - Houston, Texas
I was very pleased with the courtesy and work of Mr. Smith. He was exceptional in explaining and correcting the problem and thereby gained my trustI . I request he be my mechanic in all future service requests. I had a great experience working with Mr. Ben Smith.
Richard

Richard

19 years of experience
203 reviews
Richard
19 years of experience
Ram ProMaster 1500 - Check Engine Light is on - Bonita Springs, Florida
Prompt, polite and personal. Took the time to explain the process and his recommendations. 2 thumbs up
Michael

Michael

23 years of experience
37 reviews
Michael
23 years of experience
Ford F-150 - Check Engine Light is on - Federal Way, Washington
Very helpful and explained everything and what needs to be addressed. I feel informed and confident in Mike’s assessment and look forward to him performing services on my vehicle.
Rigoberto

Rigoberto

9 years of experience
650 reviews
Rigoberto
9 years of experience
Honda Civic - Check Engine Light is on - Chicago, Illinois
Rigoberto came on time & quickly diagnosed the problem- rats chewed thru wiring near the battery. He wasn’t able to fix it himself bc of parts, but gave me recommendations on where to go & how to not have the dealership sell me services that are not needed.

More related articles

How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Shutterstock.com Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....
P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance...

Related questions

Q: P2006 code is present in the computer.

Hi there. With having the code P2006 present, check the intake wiring to the runner control and see if there is a good connection. Also, the runners in the intake could be clogged and needs cleaned out. A leaking or...

Q: Transmission shift solenoids

Hi there, thanks for writing in. Your particular car is very prone to complete transmission failure, so I would not personally attempt to make repairs to the transmission, as it likely won't fix the problem, or may act simply as...

Q: Crank no start - 2003 Dodge Grand Caravan

Hi. Some of the codes you have will cause drivability problems and may cause the van not to start. The code p0118 deals with your coolant temperature sensor and a bad coolant temperature sensor will cause the car not to...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1-800-701-6230 · hi@yourmechanic.com