AutoCodes – Subaru – P0418 Subaru

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

Quick Answer

An air pump is used on the vehicle to lower tail pipe emissions on start-up. Common causes include Faulty Air Pump inoperative, Air bypass solenoid harness is open or shorted, Air bypass solenoid circuit poor electrical connection. 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 Subaru indicates Secondary Air Injection System Relay 'A' Circuit Malfunction.
Common causes: Common causes include Faulty Air Pump inoperative, Air bypass solenoid harness is open or shorted, Air bypass solenoid circuit poor electrical connection.
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.

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Code Popularity 10,356

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Apr 18, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0418 Subaru Description

An air pump is used on the vehicle to lower tail pipe emissions on start-up. The Powertrain Control Module (PCM) grounds the Air pump relay control circuit which energizes the Air pump. The PCM also grounds the Air combination valve vacuum control solenoid circuit, which energizes the Air vacuum control solenoid. Vacuum is then applied to both Air combination valve diaphragms which opens the shut off valves. The PCM enables both circuits simultaneously when Air system operations id desired. When the AIR system is active, then Air pump forces fresh air into the exhaust stream in order to accelerate catalyst operation. The AIR combination valves replace the conventional check valves. When the AIR system is inactive the shut off valves prevent air flow in either direction.

OBDII Code P0418 Subaru - Secondary Air Injection System Relay 'A' Circuit Malfunction - AutoCodes.com — P0418 Subaru Code - Secondary Air Injection System Relay 'A' Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC P0418 Subaru?

Faulty Air Pump inoperative
Air bypass solenoid harness is open or shorted
Air bypass solenoid circuit poor electrical connection

How to Fix the DTC P0418 Subaru?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0418 Subaru code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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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 Subaru Code

1. What are the common symptoms of OBDII code P0418 in a Subaru related to the Secondary Air Injection System Relay 'A' Circuit Malfunction?

- Common symptoms include the check engine light illuminating, rough idling, decreased engine performance, and potential engine stalling.

2. What are the possible causes of OBDII code P0418 in a Subaru?

- The code P0418 in a Subaru can be triggered by a faulty Secondary Air Injection System Relay 'A', a damaged relay connector, wiring issues, or a malfunctioning secondary air injection pump.

3. How can I diagnose the Secondary Air Injection System Relay 'A' Circuit Malfunction in my Subaru?

- Diagnosis involves using an OBDII scanner to retrieve the trouble code, inspecting the relay and its connector for any visible damage, and checking the wiring for continuity and proper connection.

4. Can I continue driving my Subaru with OBDII code P0418 triggered?

- While the vehicle may still be operational with the code triggered, it is not recommended to ignore the issue, as it can lead to further damage to the engine or emissions system over time.

5. What are the potential repair options for OBDII code P0418 in a Subaru?

- Repair options include replacing the faulty Secondary Air Injection System Relay 'A', repairing or replacing damaged wiring or connectors, and ensuring proper connection and functioning of the secondary air injection pump.

6. Are there any DIY tips for addressing OBDII code P0418 in a Subaru?

- DIY enthusiasts can start by checking the relay and its connector for any visible damage, ensuring all connections are secure, and inspecting the wiring for any signs of wear or corrosion before considering professional help.

7. How important is it to address OBDII code P0418 promptly in a Subaru?

- Promptly addressing the code is crucial to prevent potential damage to the engine, emissions system, or catalytic converter, as the secondary air injection system plays a vital role in reducing emissions during cold starts.

8. Can weather conditions affect the triggering of OBDII code P0418 in a Subaru?

- Extreme weather conditions, especially cold temperatures, can exacerbate issues related to the secondary air injection system, potentially leading to the triggering of code P0418 in a Subaru.

9. Is it necessary to reset the ECU after repairing OBDII code P0418 in a Subaru?

- It is recommended to reset the ECU after repairing the issue to clear the trouble code and ensure proper monitoring of the system for any recurring faults.

10. How can I prevent OBDII code P0418 from reoccurring in my Subaru after repair?

- To prevent the code from reoccurring, regular maintenance of the secondary air injection system, including checking the relay, connectors, and wiring, is essential. Additionally, driving habits that minimize cold starts can help reduce the strain on the system.