Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that a part in your car that helps clean the air coming out of the engine is stuck open. It's like a door that should close sometimes but is stuck open, letting too much air in.
The secondary air injection system helps reduce emissions by injecting air into the exhaust stream. The switching valve controls this air flow, and if it's stuck open, it can cause problems.
The P140D code indicates that the solenoid-actuated switching valve in the secondary air injection system is not closing as it should. This can lead to incorrect air flow into the exhaust, affecting emissions and engine performance.
• Check Engine Light is on
• Failed emissions test
• Rough engine idle
• Faulty switching valve
• Electrical issues with the solenoid
• Wiring problems or poor connections
Solenoid: An electromechanical device that converts electrical energy into mechanical movement.
Switching Valve: A valve that controls the flow of air or fluid in a system.
• Use an OBD-II scanner to confirm the code
• Inspect the switching valve for proper operation
• Check the solenoid and related wiring for damage or disconnections
• Replace the faulty switching valve
• Repair or replace damaged wiring
• Test the solenoid and replace if necessary
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $400
Moderate
• BMW 3 Series
• Audi A4
• Volkswagen Passat
• Regular maintenance and inspections
• Ensure proper electrical connections
• Use high-quality replacement parts
Emission Control System Issue
• Have the code diagnosed and repaired promptly to avoid emissions issues.
• Consider using a professional mechanic if you're not experienced with vehicle repairs.
Check with your vehicle manufacturer for warranty coverage on emissions-related components.
This code has been commonly associated with issues in vehicles with complex emission control systems, particularly in European models.
Moderate – While the vehicle may still run, emissions and performance can be affected.
Driving with a malfunctioning emission system may be illegal in some areas due to environmental regulations.
• Engine at operating temperature
• Vehicle in idle or low-speed operation
The secondary air injection switching valve is typically located near the engine or exhaust manifold.
Q: Can I drive my car with a P140D code?
A: It's possible to drive, but it's not recommended as it may affect emissions and engine performance.
Q: How do I reset the Check Engine Light after fixing the issue?
A: Use an OBD-II scanner to clear the code after repairs are completed.
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Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal 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.