Open circuit, chafed wire or corroded connector in the throttle position sensor or idle switch wiring; Dirty or carbon-fouled throttle body causing the valve to stick slightly open; Worn or faulty throttle position sensor or idle switch inside the throttle housing or actuator; Faulty throttle valve actuator or motor, or a failed adaptation; Unmetered air from a split intake hose or leaking vacuum line upsetting idle control; Throttle cable or linkage binding or misadjusted (on models with a cable-operated throttle); Fault within the engine control unit.

P1505

Closed Throttle Position Does Not Close Open Circuit.

Volkswagen
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
5: AreaVehicle speed, idle control and auxiliary inputs
05: FaultThe specific fault in that area

What it means

On a Volkswagen, P1505 means the engine control unit has detected that the throttle valve is not reaching or holding its closed (idle) position, with the fault pointing to an open circuit in the throttle position or idle switch signal. The control unit compares the commanded idle position with the feedback from the throttle position sensor or idle switch and finds it implausible. Exact wiring and sensor layout depend on the model and engine, so check the specific wiring diagram.

Symptoms

Engine management warning light on
Unstable, high or hunting idle speed
Engine stalling or struggling when coming to rest
Poor or hesitant throttle response
Engine running in a limited-performance or default mode
Idle speed changing when electrical loads are switched on

Possible causes

Open circuit, chafed wire or corroded connector in the throttle position sensor or idle switch wiringlikely
Dirty or carbon-fouled throttle body causing the valve to stick slightly openlikely
Worn or faulty throttle position sensor or idle switch inside the throttle housing or actuatorlikely
Faulty throttle valve actuator or motor, or a failed adaptationpossible
Unmetered air from a split intake hose or leaking vacuum line upsetting idle controlpossible
Throttle cable or linkage binding or misadjusted (on models with a cable-operated throttle)possible
Fault within the engine control unitrare

How to diagnose

Read all stored codes and freeze frame data, noting engine temperature, speed and load when the fault set, then check for related throttle or idle codes
Visually inspect the throttle body wiring, connector and loom for damage, corrosion, loose pins or rubbing
Look at the throttle body for carbon build-up and check that the valve moves freely and returns fully closed by hand where safe and applicable
Inspect intake hoses, joints and vacuum lines for leaks or splits
View live data for throttle position or idle switch status and check it changes smoothly and plausibly from closed to open
Check the sensor supply, reference voltage and signal wires for continuity and shorts using the wiring diagram for the specific model
Check cable or linkage movement and adjustment if the model uses a cable throttle
Clear the code, carry out the throttle adaptation or basic setting procedure for that engine, and retest

How to fix

Repair or replace damaged wiring, and clean or replace corroded connectors
Clean the throttle body with a suitable cleaner, following the manufacturer's procedure, then carry out the adaptation
Replace the throttle position sensor, idle switch or complete throttle body if it is faulty
Replace the throttle actuator assembly if it fails to close or move correctly
Repair intake leaks by replacing split hoses or perished seals
Adjust or free off the throttle cable or linkage, and replace the engine control unit only if all other causes are ruled out

Can I keep driving?

Medium severity

The car can usually be driven short distances, but idle and throttle response may be poor or the engine may stall, which can be unsafe in traffic. Get it diagnosed soon and avoid long journeys until it is fixed.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.