P0418 Code: Secondary Air Injection System Relay A Circuit Malfunction
🟠 Moderate severity · drivable
Drivable — this affects cold-start emissions, not drivability. Fix it before your next emissions test.
What P0418 means
The relay that powers the secondary air injection pump has an electrical fault, so the pump can't run when commanded.
Symptoms
- Check engine light is on
- Possible failed emissions test
- No driving symptoms
Common causes
- most common: Faulty secondary air pump relay
- common: Damaged wiring or blown fuse
- less common: Faulty air pump drawing too much current
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Replace the secondary air pump relay | Yes | $20–60 |
| Check the fuse and repair damaged wiring | Yes | $0–50 |
Frequently asked questions
Can I drive with a P0418 code?
Yes. It only affects cold-start emissions, not drivability.
What is the most common cause of P0418?
A faulty secondary air pump relay.
How much does it cost to fix a P0418?
Typically $20–$60 for a new relay.
Related codes
P0410
P0410 Code: Secondary Air Injection System Malfunction
P0411P0411 Code: Secondary Air Injection System Incorrect Flow Detected
P0412P0412 Code: Secondary Air Injection (AIR) Switching Valve A Circuit Malfunction
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.