Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there's a problem with the part of the car that helps control how fast the engine runs when you're not pressing the gas pedal. It's like the car's 'breathing' system isn't working right on one side of the engine.
The P159B code is triggered when the Engine Control Module (ECM) detects a malfunction in the idle speed control valve on bank 2 of the engine.
The idle speed control valve is responsible for maintaining the engine's idle speed by regulating the amount of air entering the engine. A diagnostic error in this valve indicates that it is not functioning correctly, affecting the engine's ability to maintain a stable idle speed.
• Unstable or fluctuating idle speed
• Engine stalling at idle
• Check Engine Light illuminated
• Faulty idle speed control valve
• Wiring issues or poor electrical connections
• ECM software issues
ECM: Engine Control Module, the computer that controls the engine's functions.
Idle Speed Control Valve: A component that regulates the engine's idle speed by controlling air flow.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connections to the idle speed control valve.
• Test the idle speed control valve for proper operation.
• Replace the faulty idle speed control valve.
• Repair or replace damaged wiring or connectors.
• Update or reprogram the ECM if necessary.
• OBD-II scanner
• Multimeter
• Screwdriver set
$150 - $400
Moderate
• BMW 5 Series
• Mercedes-Benz E-Class
• Audi A6
• Regular maintenance and inspection of engine components
• Keep electrical connections clean and secure
• Update vehicle software as recommended by the manufacturer
Engine Performance
• Avoid driving with an unstable idle as it can lead to stalling.
• Have the vehicle inspected by a professional mechanic.
Check with the vehicle manufacturer for warranty coverage on emissions-related components.
This code has been associated with idle control issues in various vehicle models, often related to wear and tear or electrical faults.
Moderate – It should be addressed soon to avoid potential stalling and drivability issues.
Driving with this issue may lead to engine stalling, which can be dangerous. Address the problem promptly.
• Engine at operating temperature
• Vehicle in park or neutral
The idle speed control valve is typically located on the throttle body of the engine.
Q: Can I drive my car with a P159B code?
A: It's not recommended to drive for long periods with this code as it can cause engine stalling.
Q: How do I reset the Check Engine Light after fixing the issue?
A: Use an OBD-II scanner to clear the code after the repair is completed.
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Universal · Digital multimeter
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Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
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Fitment Required · Vehicle-fitment part
Relevant for airflow, fuel-trim, and intake-metering faults after confirming the sensor is actually at fault.
Airflow and fuel-trim codes can involve the mass air flow sensor after proper diagnosis.
Verify the sensor design and fitment for your exact vehicle.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.