Faulty idle speed control valve solenoid (open or shorted winding); Damaged or corroded electrical connector at the idle speed control valve; Broken, chafed, or shorted wiring in the valve control circuit; Poor ground connection for the idle speed control valve circuit; Failed engine control module (DME) driver for the solenoid circuit (rare); Carbon buildup or mechanical binding inside the idle speed control valve causing abnormal current draw

DTC codes / BMW codes / P1509

P1509 · BMWIdle Speed Control Valve Opening Solenoid Control Circuit Electrical

P1509 on BMW vehicles indicates that the engine control module (DME) has detected an electrical fault in the control circuit for the idle speed control valve's opening solenoid. The computer monitors the circuit for expected voltage or current and flags the code when the signal falls outside the valid range, which can prevent the valve from properly regulating idle speed.

SystemPowertrain

Code typeBMW specific

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Unstable or fluctuating idle speed, sometimes surging or dipping
Engine may stall when coming to a stop or when the transmission is shifted into gear
Rough idle quality, especially when the engine is cold
Occasional hesitation or stumble during acceleration from a stop

Common causes, most likely first

Faulty idle speed control valve solenoid (open or shorted winding)
Damaged or corroded electrical connector at the idle speed control valve
Broken, chafed, or shorted wiring in the valve control circuit
Poor ground connection for the idle speed control valve circuit
Failed engine control module (DME) driver for the solenoid circuit (rare)
Carbon buildup or mechanical binding inside the idle speed control valve causing abnormal current draw

How to diagnose and fix it

Scan all modules for stored and pending codes, and record freeze-frame data to confirm the fault conditions
Visually inspect the idle speed control valve connector and wiring for corrosion, damage, or loose pins
Measure the resistance of the valve solenoid with a multimeter and compare to BMW specifications
Check for battery voltage and ground signals at the valve connector with the key on, using a wiring diagram
Perform a voltage drop test on the ground circuit and repair any excessive resistance
If the circuit tests good, remove and clean the idle speed control valve, then recheck operation
Replace the idle speed control valve if electrically faulty, clear codes, and verify idle stability

What BMW technicians check before replacing the valve

A dirty throttle body or intake carbon can cause the DME to set P1509 indirectly by forcing the idle valve to compensate beyond its normal range, so cleaning the throttle body is often part of the diagnostic process.
The idle speed control valve on many BMW engines is a two-winding unit; P1509 refers specifically to the opening solenoid circuit, so testing both windings and comparing resistance values is critical.
Wiring harness damage near the intake manifold or under the engine cover is a common cause that is frequently overlooked when only the valve itself is replaced.
A weak battery or charging system fault can cause erratic solenoid operation and set P1509 without any defect in the valve or its wiring, so always verify battery voltage and alternator output first.
After repairs, a idle relearn or adaptation reset via a BMW-specific scan tool is often required to restore smooth idle and prevent the code from returning.

Can I keep driving with P1509?

You can usually drive the car with P1509, but expect an unstable idle that may cause stalling at low speeds, so avoid heavy traffic and keep your foot ready on the brake. Have the fault diagnosed soon to prevent worsening drivability and possible catalytic converter damage from rich running.

Tools that help

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Guidance is general and written for BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.