P0519

What it means

P0519 means the engine control unit has found that the idle speed control system is not holding or reaching the target idle speed. It sets when actual idle speed stays out of step with the commanded speed, or when the idle air control commands do not give the expected response. The fault can lie in the idle air control valve or throttle body, an air leak, or a sensor or wiring problem, and the layout depends on the engine.

Symptoms

• Idle speed too high, too low or hunting up and down
• Engine stalls or nearly stalls when coming to rest or when put into gear
• Rough idle, especially when the engine is cold or when loads such as air conditioning switch on
• Hard starting or the engine dying just after start
• Malfunction indicator lamp on
• Poor throttle response at very low speeds

Possible causes

• Dirty or carbon-fouled throttle body or idle air passages restricting airflow at idlelikely
• Unmetered air leak, such as a split intake hose, cracked manifold gasket or perished vacuum hoselikely
• Faulty or sticking idle air control valve or electronic throttle actuatorlikely
• Damaged wiring or poor connector contact at the idle control valve, throttle body or related sensorspossible
• Faulty sensor feeding the idle strategy, such as the mass airflow, manifold pressure, throttle position or coolant temperature sensorpossible
• Throttle body relearn or adaptation not completed after cleaning, replacement or battery disconnectionpossible
• Fault in the engine control unit itselfrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine temperature, load and idle speed when the fault set, and address any other codes first
2. Visually inspect the intake pipework, vacuum hoses, breather hoses and connectors for splits, loose clips and damage
3. Check the wiring and connectors at the idle control valve or throttle body for corrosion, bent pins, chafing and a secure fit
4. Compare the live data for commanded idle speed against actual idle speed, and check the airflow or manifold pressure readings and the coolant temperature reading are sensible
5. Inspect the throttle body bore and idle air passage for carbon build-up and check the throttle plate or valve moves freely
6. Test for air leaks with the engine idling, using a suitable smoke test, rather than guessing
7. Command the idle valve or throttle actuator with a diagnostic tester and check that idle speed responds, then test its supply, earth and signal as per the manufacturer's data
8. Where the model uses one, confirm that the throttle adaptation or idle relearn procedure has been completed and check the manufacturer's data for the correct method

How to fix

• Clean the throttle body and idle air passages using the method the manufacturer recommends, then carry out any required relearn
• Repair or replace leaking hoses, gaskets or intake pipework
• Replace the idle air control valve or throttle body assembly if it sticks or fails its response test
• Repair damaged wiring or connectors found in the control circuit
• Replace any faulty sensor confirmed by testing, then clear the code and check it does not return
• Carry out the idle or throttle adaptation procedure after any repair so the control unit relearns the correct values

Can I keep driving?

Nearby codes

• P0518GenericIdle Air Control Circuit Intermittent
• P051AGenericCrankcase Pressure Sensor A Circuit