Why is my car idling so low?

Carbon buildup on the throttle body or a stuck idle air control valve is a common cause. The engine cannot pull enough air at idle, the ECU cannot bring RPM up to target, and you feel it as a shaky, sometimes stalling idle.

Will cleaning the throttle body fix P0506?

Often yes, but only if you also perform the idle relearn afterwards. Without the relearn, the ECU keeps commanding the throttle to the position it learned when the bore was dirty, and the symptom returns within a day or two.

Why does my engine stall when the AC turns on?

The AC compressor adds load to the engine at idle. A healthy idle control system raises RPM to compensate. When P0506 is set, the system can no longer pull that extra air, so the engine loses RPM and may stall.

Is P0506 the opposite of P0507?

Yes. P0506 means the engine idles too low; P0507 means it idles too high. Both point to a problem with how the ECU controls idle airflow, but the causes are different. P0506 usually points to restriction; P0507 usually points to a leak or stuck-open valve.

P0506: Idle Air Control System RPM Lower Than Expected

Quick Answer

Safe to drive (short-term)

P0506 means the engine is idling at a lower RPM than the ECU expects, typically 100 RPM or more below target, and the ECU cannot bring it back up. The opposite of P0507, this code is usually caused by carbon buildup on the throttle body restricting airflow, a partially clogged idle air control passage, or a vacuum hose pinched or blocked rather than leaking.

Severity: Moderate · Fuel System
Estimated repair cost: From €5 to €550+, varies by vehicle

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What does P0506 mean?

P0506 is a fuel system-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0506 and illuminates the check engine light.

Where it is on the car

Air filter box
Mass airflow sensor (MAF)
Throttle body and throttle position sensor
Intake manifold and MAP sensor
Engine (cylinder head)

Idle speed depends on the air that passes the throttle. A dirty throttle body, or a sticking idle air valve on older cars, is a common cause.

What are the symptoms of P0506?

If your vehicle has triggered P0506, you may notice one or more of these symptoms:

Idle noticeably lower than normal (500 RPM or less)
Engine stalls at idle or when coming to a stop
RPM dips and recovers when the AC compressor engages
Rough or shaky idle with the engine in gear (automatic)
Check engine light on

What causes P0506?

Here are the most common causes of P0506:

Carbon-fouled throttle body restricting airflow at idle
: high
Clogged or stuck idle air control valve
: high
Blocked PCV passage or restricted idle air bypass
: medium
Faulty coolant temperature sensor causing wrong idle target
: low

Is it safe to drive with P0506?

Generally yes, for short-term driving. The engine idles lower than the ECU target and may stall at junctions or when the AC compressor engages. Drive cautiously and fix within a couple of weeks to avoid being stranded by an unexpected stall.

How do you diagnose P0506?

Follow these steps to pinpoint the root cause of P0506:

Read freeze-frame data and confirm idle RPM at the time the code set. Engine RPM is standard OBD2 live data; the ECU's commanded idle target usually needs manufacturer-level software
Remove the intake boot and inspect the throttle plate and bore for carbon buildup. Heavy deposits restrict airflow even with the plate fully closed
Clean the throttle body with throttle body cleaner and a soft cloth. On electronic throttle bodies, do not force the plate open by hand; open it with the ignition-on procedure or an output test in manufacturer-level software instead
If equipped with a separate idle air control valve, remove and clean it, then check that it moves through its full range (an output test usually needs manufacturer-level software)
After cleaning, perform the manufacturer's idle or throttle relearn procedure (on many cars this is an adaptation run with manufacturer-level software). Without a relearn, the ECU continues to command the same restrictive throttle position

How much does P0506 cost to fix?

Repair costs for P0506 vary depending on the root cause and your vehicle. Here are typical estimates:

Repair	Parts Cost	Labor Cost	Total Estimate	DIY Difficulty
Clean throttle body	€5–€15	€0–€60	€5–€75	Easy
Clean or replace idle air control valve	€60–€200	€40–€100	€100–€300	Moderate
Replace throttle body assembly	€150–€400	€60–€150	€210–€550	Professional

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

Full repair guides

P0506 on specific vehicles

P0506 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

Toyota

Toyota Camry

2002-2018

Older Camrys with the 2AZ-FE and 2GR-FE use an electronic throttle body that fouls with carbon over 80,000-120,000 km. Toyota's idle relearn after cleaning requires the engine to idle for five minutes with the AC off, all accessories off, and the throttle untouched.

P0506 on Volkswagen

Volkswagen Golf

See Volkswagen-specific causes & cost

Ford

Ford Focus

2005-2014

Mk2 Focus with the 1.6 Duratec is prone to a sticky electronic throttle body causing P0506 along with surging or stalling at idle. Cleaning the throttle body on these engines has to be followed by a software-driven relearn that resets the adaptive idle values.

P0506 on Honda

Honda Civic

See Honda-specific causes & cost

These codes are often seen alongside P0506 or indicate related issues:

Common questions about P0506

Why is my car idling so low?: Carbon buildup on the throttle body or a stuck idle air control valve is a common cause. The engine cannot pull enough air at idle, the ECU cannot bring RPM up to target, and you feel it as a shaky, sometimes stalling idle.
Will cleaning the throttle body fix P0506?: Often yes, but only if you also perform the idle relearn afterwards. Without the relearn, the ECU keeps commanding the throttle to the position it learned when the bore was dirty, and the symptom returns within a day or two.
Why does my engine stall when the AC turns on?: The AC compressor adds load to the engine at idle. A healthy idle control system raises RPM to compensate. When P0506 is set, the system can no longer pull that extra air, so the engine loses RPM and may stall.
Is P0506 the opposite of P0507?: Yes. P0506 means the engine idles too low; P0507 means it idles too high. Both point to a problem with how the ECU controls idle airflow, but the causes are different. P0506 usually points to restriction; P0507 usually points to a leak or stuck-open valve.

Read our detailed guides

Scan your car with Skanyx to diagnose P0506

Your car logged P0506. Skanyx reads it on a standard OBD2 adapter (Bluetooth LE on iPhone), tells you whether it is safe to keep driving, and shows the €5-€550 repair range so you know the number before a shop quotes you. Free on iPhone and Android, and you do not need to be a mechanic to read it.