Fault code P0505 – a step-by-step guide to diagnosing and fixing it

Error code P0505 is displayed and the check engine light is on - what does this mean?

DTC P0505 is recognized by the OBD system when there is a problem with the idle speed control system. This error code indicates that the engine control unit cannot regulate the idle speed properly. Different manufacturers may have slightly different interpretations of this code, but it always refers to the idle speed control system.

What causes can this error code have?

• Defective idle control valve (IAC valve)
• Dirty or damaged mass air flow sensor
• Leak in the intake system
• Defective throttle valve sensor
• Damaged cable or loose plug connections
• Clogged or dirty throttle valve
• Defective vacuum hoses
• Problems with the engine control unit
• Dirty air filter
• Faulty spark plugs or ignition coils

What symptoms occur in parallel with fault code P0505?

• Irregular idling: The engine runs irregularly at idle or fluctuates in speed
• Engine stalling: The vehicle stalls when idling or when coming to a stop
• Increased fuel consumption: The engine consumes more fuel than usual
• Starting problems: The vehicle is difficult to start, especially when the engine is cold
• Jerking when driving: The engine jerks or stutters while driving
• Poor throttle response: Delayed response when accelerating

How to fix the problem of error code P0505?

• Repairing the P0505 error code requires a systematic approach to identifying and eliminating the underlying cause.
• Clean or replace the idle control valve: Remove the IAC valve, clean it thoroughly with brake cleaner or replace it completely if defective to restore proper airflow at idle
• Clean the throttle valve: Dismantle the throttle valve and remove carbon deposits with special cleaner, then have it recalibrated
• Check and clean the mass air flow sensor: Treat the MAF sensor with special cleaner or replace if damaged to ensure correct air flow measurement
• Check the intake system for leaks: Check all hoses, seals and connections between the air filter and engine and replace defective parts
• Check electrical connections: Check all cables and plugs on the idle control valve and throttle sensor for corrosion or breakages and repair them
• Maintain air filter and ignition components: Replace dirty air filter and check spark plugs and ignition coils for proper function