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 clean the air before it goes out of the car's exhaust on one side of the engine.
The secondary air injection system helps reduce emissions by injecting air into the exhaust stream to help burn off excess fuel. Bank 2 refers to the side of the engine opposite Bank 1.
The P1421 code indicates that the secondary air injection system is not functioning properly on Bank 2 of the engine. This system is responsible for injecting fresh air into the exhaust stream to help reduce emissions during cold starts. The ECU has detected a malfunction in this system, which could be due to a variety of reasons such as a faulty air pump, blocked air lines, or a defective check valve.
• Check Engine Light is on
• Increased emissions
• Failed emissions test
• Rough idle during cold start
• Faulty secondary air injection pump
• Clogged or leaking air injection hoses
• Defective check valve
• Faulty air pump relay
• Electrical issues in the air injection system
ECU: Engine Control Unit, the computer that controls engine functions.
Check Valve: A valve that allows air to flow in one direction only, preventing backflow.
• Use an OBD-II scanner to confirm the P1421 code.
• Inspect the secondary air injection pump and hoses for damage or leaks.
• Check the operation of the check valve and relay.
• Test the electrical connections and wiring of the air injection system.
• Replace the faulty secondary air injection pump.
• Repair or replace damaged or clogged hoses.
• Replace the defective check valve.
• Repair any electrical issues or replace the faulty relay.
• OBD-II scanner
• Multimeter
• Vacuum pump
• Basic hand tools
$200 - $600
Moderate
• BMW 3 Series
• Mercedes-Benz C-Class
• Audi A4
• Regularly inspect and maintain the air injection system.
• Ensure proper electrical connections.
• Keep the exhaust system clean and free of blockages.
Emission Control System Issue
• Get the system checked by a professional to avoid increased emissions.
• Avoid ignoring the check engine light as it may lead to more severe issues.
• Regular maintenance can prevent this issue.
Check with your vehicle's manufacturer warranty; emissions components may be covered under extended warranties.
This code has been more common in vehicles with aging emissions systems, particularly in models with complex air injection systems.
Moderate – Addressing this issue is important for emissions compliance and optimal vehicle performance.
Driving with a malfunctioning emissions system may violate local emissions laws and contribute to environmental pollution.
• Engine cold start
• Vehicle at operating temperature
The secondary air injection pump is typically located near the front of the engine bay, with hoses running to the exhaust manifold.
Q: Can I drive with a P1421 code?
A: While you can drive with this code, it is recommended to fix it soon to avoid increased emissions and potential engine performance issues.
Q: How does the secondary air injection system work?
A: It injects fresh air into the exhaust stream to help burn off excess fuel and reduce emissions during the engine's cold start phase.
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