The P0418: Secondary Air Injection System Relay ‘A’ Circuit Malfunction code indicates that the engine control module (ECM) has detected an issue with the secondary air injection system relay A circuit. This relay controls the operation of the secondary air injection pump, which helps reduce emissions by injecting air into the exhaust. A malfunction in relay A can cause increased emissions and affect engine performance.
P0418 – Quick Overview
| Meaning | P0418: Secondary Air Injection System Relay ‘A’ Circuit Malfunction |
| Is it serious? | Yes, this code can cause increased emissions and may affect the vehicle’s engine performance, potentially leading to failed emissions tests. |
| Possible causes | – Faulty relay A – Wiring or connector issues – Faulty relay control circuit |
| How to diagnose? | – Test relay A for proper function – Inspect wiring and connectors for damage – Check the relay control circuit for faults |
P0418 Meaning
The P0418: Secondary Air Injection System Relay ‘A’ Circuit Malfunction code means that the ECM has detected a fault in relay A of the secondary air injection system. This relay controls the operation of the air injection pump, which helps reduce emissions. If relay A or its circuit fails, the secondary air system may not function properly, leading to higher emissions and possibly affecting engine performance.
Step-by-step diagnostic guide
Follow these steps to diagnose and resolve the P0418 code by addressing potential causes one by one.
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for other related codes that might provide more insight into the secondary air injection system or electrical issues. | OBD-II Scanner |
| Test Relay A for Proper Function | Use a multimeter to test the functionality of relay A. Check the relay’s operation against manufacturer specifications to ensure it is functioning correctly. | Multimeter, Manufacturer’s Specifications |
| Inspect Wiring and Connectors for Damage | Inspect the wiring and connectors leading to relay A for signs of damage, corrosion, or loose connections. Repair or replace any damaged wiring as necessary. | Flashlight, Wiring Repair Kit |
| Check the Relay Control Circuit for Faults | Test the control circuit responsible for switching relay A. If the control circuit is faulty, the relay may not function properly. Ensure the ECM is sending the correct signals to the relay. | OBD-II Scanner, Multimeter |
| Replace Faulty Components | If relay A, the wiring, or the control circuit is found to be faulty, replace the necessary components to restore proper system function. | Replacement Relay A, Wiring Components |
| Clear the Code and Test Drive | After completing repairs, clear the P0418 code using an OBD-II scanner. Test drive the vehicle to ensure the issue is resolved and that the system is functioning properly. | OBD-II Scanner, Vehicle Owner’s Manual |
| Recheck for Codes | After the test drive, re-scan the vehicle to confirm that the P0418 code has not returned. If the code reappears, further diagnosis may be required. | OBD-II Scanner |
This diagnostic guide will help you resolve the P0418 code by ensuring that relay A and its related circuit are functioning correctly, allowing the secondary air injection system to reduce emissions and maintain proper engine performance.
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I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko