P0506

What it means

P0506 means the engine control unit has seen the idle speed settle below the target it is commanding, and it could not bring it back up within the limits of its idle control. This usually points to extra air or too little air control at idle, or an extra load on the engine, rather than a single fixed fault. The exact idle strategy and tolerance vary by manufacturer and engine.

Symptoms

• Low or hunting idle speed
• Rough idle that may feel as if the engine is about to stall
• Engine stalls when coming to a stop or when shifting into gear
• Hesitation or stumbling when pulling away from rest
• Engine warning light on
• Idle drops further when electrical loads, air conditioning or power steering are used

Possible causes

• Dirty or carbon-fouled throttle body or idle air passages restricting airflow at idlelikely
• Intake air leak (split hose, cracked intake pipe, loose clip or worn manifold gasket) upsetting the air-fuel mixturelikely
• Faulty or sticking idle air control valve or electronic throttle actuator, on engines that use onepossible
• Faulty PCV system component or vacuum leak at a brake servo or other vacuum hosepossible
• Extra engine load at idle, such as a failing alternator, air conditioning compressor or power steering pumppossible
• Fuel delivery or ignition weakness (worn spark plugs, weak coil, clogged injector, low fuel pressure) causing the engine to run unevenly at idlepossible
• Faulty sensor feeding the idle strategy, such as the mass airflow, throttle position or coolant temperature sensorrare

How to diagnose

1. Read all stored and pending codes and review the freeze frame data for engine temperature, load and speed when the fault set
2. Check the engine for obvious air leaks: inspect intake hoses, clips, the PCV hose and vacuum lines for splits, perishing or loose fittings
3. Look over the wiring and connectors at the throttle body, idle control valve and airflow sensor for damage, corrosion or poor contact
4. Inspect the throttle body bore and idle air passages for carbon build-up
5. Compare live data at idle: target against actual idle speed, short and long term fuel trims, airflow reading and throttle angle. High positive fuel trims at idle suggest an air leak
6. Smoke test the intake system to find leaks that cannot be seen
7. Check for added load: alternator output, air conditioning and power steering operation, and confirm the idle changes when each is switched on
8. Check spark plugs, coils and fuel pressure if the idle is rough, following the procedure for that engine

How to fix

• Clean the throttle body and idle air passages using a method suitable for the engine, then carry out the throttle adaptation or relearn if the manufacturer requires it
• Repair or replace leaking hoses, gaskets or the PCV components found during the smoke test
• Replace a faulty idle air control valve or throttle actuator, then perform any required adaptation
• Repair or replace a failing alternator, compressor or power steering pump that is overloading the engine
• Replace worn spark plugs, weak coils or blocked injectors, and replace any sensor shown to be reading incorrectly
• Where a manufacturer bulletin identifies an outdated engine control software as a cause for the specific model, have it updated to the latest approved calibration

Can I keep driving?

This code for other makes

• P0506AudiDefective or sticking Idle Air Control Motor, Intake Manifold Vacuum leaks, Carbon buildup in the Throttle Body air passages, Defective Power Steering Pressure Switch

Nearby codes

• P0505GenericIdle Control System
• P0507GenericIdle Control System RPM - Higher Than Expected