P0418 Code - Secondary Air Injection System Relay 'A' Circuit Malfunction

Quick Answer

The P0418 code indicates a malfunction in the Secondary Air Injection System Relay 'A' circuit. Common causes include Faulty Relay: The primary cause of this code is a faulty secondary air injection system relay 'A', Wiring Issues: Corrosion, damage, or loose connections in the wiring associated with the relay circuit can also trigger this code, Defective Pump: A malfunctioning secondary air injection pump can cause the relay 'A' circuit to malfunction. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means

P0418 indicates Secondary Air Injection System Relay 'A' Circuit Malfunction.

Common causes

Common causes include Faulty Relay: The primary cause of this code is a faulty secondary air injection system relay 'A', Wiring Issues: Corrosion, damage, or loose connections in the wiring associated with the relay circuit can also trigger this code, Defective Pump: A malfunctioning secondary air injection pump can cause the relay 'A' circuit to malfunction.

Severity

Moderate - service should be scheduled soon.

Can I drive?

The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

• Description
• Common Causes
• Symptoms
• How To Fix
• Cost to Fix
• FAQs
• Comments
• Add Comment

Common Causes of P0418

Symptoms of P0418

How to Fix P0418

Cost to Fix P0418

When is the Code Detected?

Need more information about the P0418 code?

Need more information on how to fix the P0418 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0418 code diagnosed by a professional: Find a repair shop in your area

Code P0418 Information for Specific Makes

• P0418 Audi — Secondary Air Injection System Relay 'A' Circuit Malfunction
• P0418 Buick — Secondary Air Injection Pump Relay Control Circuit
• P0418 Cadillac — Secondary Air Injection Pump Relay Control Circuit
• P0418 Chevrolet — Secondary Air Injection Pump Relay Control Circuit
• P0418 Chrysler — Secondary Air Injection System Relay 'A' Circuit Malfunction
• P0418 Dodge — Secondary Air Injection System Relay 'A' Circuit Malfunction
• P0418 GMC — Secondary Air Injection Pump Relay Control Circuit
• P0418 Isuzu — Secondary Air Injection Pump Control Circuit
• P0418 Jeep — Secondary Air Injection System Relay 'A' Circuit Malfunction
• P0418 Lexus — Secondary Air Injection System Relay 'A' Circuit Malfunction
• P0418 Mercedes-Benz — Secondary Air Injection System Relay 'A' Circuit Malfunction
• P0418 Pontiac — Secondary Air Injection Pump Relay Control Circuit
• P0418 Saturn — Secondary Air Injection Pump Relay Control Circuit
• P0418 Subaru — Secondary Air Injection System Relay 'A' Circuit Malfunction
• P0418 Toyota — Secondary Air Injection System Relay 'A' Circuit Malfunction
• P0418 Volkswagen — Secondary Air Injection System Relay 'A' Circuit Malfunction

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0418 Code

1. What are the common symptoms of OBDII code P0418?

- Common symptoms of P0418 include illuminated Check Engine Light (CEL), rough idling, decreased engine performance, and increased emissions.

2. What does the OBDII code P0418 indicate about the Secondary Air Injection System Relay 'A' Circuit?

- P0418 indicates a malfunction in the relay 'A' circuit of the Secondary Air Injection System, which is responsible for reducing vehicle emissions during cold engine starts.

3. What are the potential causes of the Secondary Air Injection System Relay 'A' Circuit Malfunction (P0418)?

- Potential causes of P0418 include a faulty relay, damaged wiring or connectors in the circuit, a blown fuse, or a malfunctioning Secondary Air Injection pump.

4. How serious is the OBDII code P0418?

- While P0418 may not cause immediate harm to the vehicle, it can lead to increased emissions and potential damage to the catalytic converter over time if left unresolved.

5. Can I continue driving with OBDII code P0418 unaddressed?

- It is generally not recommended to drive with an unresolved P0418 code, as it can negatively impact engine performance and emissions, and may lead to additional issues down the line.

6. How can I diagnose the cause of OBDII code P0418 at home?

- You can start diagnosing P0418 by checking the relay, inspecting the wiring and connectors for damage, testing the fuse, and ensuring the Secondary Air Injection pump is functioning properly.

7. Is it possible to clear the OBDII code P0418 and see if it returns?

- Clearing the code may temporarily turn off the Check Engine Light, but if the underlying issue causing P0418 is not fixed, the code is likely to reappear after some driving cycles.

8. How much does it typically cost to repair OBDII code P0418?

- The cost of repairing P0418 can vary depending on the root cause, but it may range from a simple fuse replacement to a more involved relay or pump replacement, costing anywhere from $100 to $500 or more.

9. Will fixing the Secondary Air Injection System Relay 'A' Circuit Malfunction (P0418) improve fuel efficiency?

- Addressing P0418 can potentially result in improved fuel efficiency, as a properly functioning Secondary Air Injection System helps optimize engine performance and emissions control.

10. Can a DIY enthusiast with basic mechanical skills repair OBDII code P0418?

- Depending on the specific cause, a DIY enthusiast with basic mechanical skills may be able to address P0418 by replacing a fuse or relay, but more complex issues may require professional diagnosis and repair.