P0418: Secondary Air Injection System Relay A Circuit
6 vehicles · 2 makes · $100-$4,000 repair
Most Reported On
P0418 is an OBD-II diagnostic trouble code meaning “Secondary Air Injection System Relay A Circuit.” This code means the Engine Control Module detected a fault in the control circuit for Secondary Air Injection (AIR) System Relay 'A'. The secondary air injection system pumps fresh air into the exhaust during cold starts to help the catalytic converter heat up faster and burn off pollutants, and Relay A switches power to that air pump. P0418 sets when the computer commands the relay but sees an abnormal voltage or no response on its control circuit. This is an emissions-related fault that may keep the air pump from running when needed. This code is most commonly reported on 2005-2013 Toyota Tundra, 2001-2009 Toyota Sequoia, and 1998-2007 Toyota Land Cruiser, plus 3 other vehicles, with repair costs ranging from $100 to $4,000.
Common Causes
Typical Repair Cost
Based on 7 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0418, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
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Vehicles Affected (6)
Secondary Air Injection Pump Failure
Secondary Air Injection System Failure (2UZ-FE)
Secondary Air Injection Pump Failure (3UR-FE/i-FORCE)
Secondary Air Injection System Failure (100-Series, 4.7L V8)
Secondary Air Injection Pump and Switching Valve Failure on 4.0L V6
Secondary Air Injection Pump/Valve Failure Triggering Limp Mode on 4.7L V8
FAQ
What does P0418 mean?
P0418 stands for "Secondary Air Injection System Relay A Circuit." This code means the Engine Control Module detected a fault in the control circuit for Secondary Air Injection (AIR) System Relay 'A'. The secondary air injection system pumps fresh air into the exhaust during cold starts to help the catalytic converter heat up faster and burn off pollutants, and Relay A switches power to that air pump. P0418 sets when the computer commands the relay but sees an abnormal voltage or no response on its control circuit. This is an emissions-related fault that may keep the air pump from running when needed.
What are the most common causes of P0418?
The most common causes of P0418 are: Faulty secondary air injection relay (Relay A), Open, shorted, or corroded relay control wiring, Poor power or ground feed to the relay, Failed secondary air injection pump (drawing wrong current), Corroded relay socket or connector, Blown fuse in the air injection circuit, Faulty ECM relay driver. The specific cause varies by vehicle.
How much does it cost to fix P0418?
Repair costs for P0418 range from $100 to $4,000, depending on the vehicle and root cause.
Which vehicles are affected by P0418?
Au7o has documented P0418 across 6 vehicle models from 2 manufacturers: Subaru, Toyota.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.