P0418 on Toyota: How to Diagnose & Fix
Secondary Air Injection System Relay A Circuit
6 Toyota models · 7 documented issues · 2 critical · $100-$4,000 repair
P0418 on Toyota by model: symptoms, diagnosis and fix
The secondary air injection pump is prone to failure due to water intrusion. The electric motor is located in the wheel well with moisture exposure, and the rubber boot covering the motor traps water, causing the pump to short circuit. This triggers check engine lights with codes P2440, P2443, P2445, P2447, P0418, or P0419. Some vehicles may enter limp mode.
Common Symptoms
- Check engine light illumination
- Jet engine noise on cold startup
- Decreased fuel economy
- Limp mode activation
- Rough idle when cold
How to Fix
Toyota issued a service bulletin for 2007-2010 models covering replacement of the entire air injection system. Repair costs range from $2,000-$4,000 for OEM replacement. Some owners opt for aftermarket bypass kits with block-off plates.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Toyota 17610-0S010 genuine secondary-air pump assembly
replace the corresponding pump only when active testing and the applicable Toyota program identify it as failed Fitment/availability: Cataloged for selected 2007-2013 Tundra applications; exact engine, side/quantity, DTC branch, VIN and …
- Toyota 17610-0S030 genuine secondary-air pump assembly
replace the program-matched pump after active-test confirmation, with all required valves, inlets, gaskets and calibration handled separately Fitment/availability: Cataloged for selected 2012-2021 4.6L/5.7L applications; on this card use…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipDIY repairs can save significantly - dealer charges $2,000-$4,000 but DIY costs are typically 50-70% less
- TipConsider OEM parts for critical components like sensors and electrical parts - aftermarket can be unreliable
- TipGet a proper diagnosis before replacing parts - similar symptoms can have different causes
The 4.7L 2UZ-FE's secondary air injection system fails due to corroded air switching valves (ASVs) and seized air pumps. Moisture enters the system and corrodes internal components. Causes check engine light with P2440/P2442 codes.
Common Symptoms
- Check engine light with P2440 or P2442 codes
- Rough idle on cold start
- Ticking or buzzing noise from air pump on startup
- Failed emissions testing
How to Fix
Replace air switching valves (Toyota 25701-50040 and 25702-50011) and air injection pump (Toyota 17610-0S010) if seized. Many owners bypass the system entirely with block-off plates since it only operates during cold start for emissions. Bypass plates available from Trail Gear or fabricated from aluminum.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Toyota 17600-0F010 secondary air injection pump assembly
replace a debris-damaged secondary-air pump after bulletin diagnosis Fitment/availability: Exact pump listed by T-SB-0230-12 Rev1 for an eligible 2005-2007 Sequoia 2UZ-FE; replace only when bulletin inspection finds debris in the pump Fi…
- Toyota 25710-50022 air switching valve assembly
replace the corresponding failed or debris-damaged air switching valve Fitment/availability: Exact air switching valve assembly listed by T-SB-0230-12 Rev1; use only on the diagnosed valve branch and confirm VIN before ordering Fitment/a…
- Toyota 25720-50011 electric air control valve No. 1
1 valve only when its bulletin diagnostic branch confirms failure or damage Fitment/availability: Exact No. 1 valve listed by T-SB-0230-12 Rev1; not interchangeable with the No.
- Toyota 25720-50020 electric air control valve No. 2
2 valve only when its bulletin diagnostic branch confirms failure or damage Fitment/availability: Exact No. 2 valve listed by T-SB-0230-12 Rev1; not interchangeable with the No.
- Toyota 89580-34012 air injection control driver
replace the air-injection control driver on the bulletin's residual-code branch Fitment/availability: Exact driver identified by T-SB-0230-12 Rev1; use only if P0418 or P2445 remains after the applicable mechanical repair and confirmatio…
- Toyota 17171-50030 intake manifold-to-head gasket No. 1
reseal both intake-manifold-to-head joints during the applicable repair Fitment/availability: Exact gasket listed by T-SB-0230-12 Rev1; bulletin quantity is two when the applicable air-injection repair requires intake-manifold removal Fi…
- Toyota 17377-50010 air tube gasket No. 4
replace disturbed air-tube seals during the bulletin repair Fitment/availability: Exact air-tube gasket listed by T-SB-0230-12 Rev1; bulletin quantity is four for the applicable repair Fitment/availability: Ships in 1-3 business days wit…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
2nd-gen Sequoias with the 5.7L 3UR-FE also suffer from secondary air injection pump failures, similar to the 1st gen but with updated part numbers. The pump seizes from internal moisture corrosion, triggering P2440-P2445 codes and check engine light.
Common Symptoms
- Check engine light with P2440-P2445 codes
- Loud buzzing or grinding on cold start
- Air pump not engaging on startup
- Failed emissions test
How to Fix
Replace secondary air injection pump (Toyota 17610-0S010 or Dorman 306-058). Replace air switching valves if corroded. Aftermarket pumps are available at lower cost. Some owners install check valves in the air line to prevent moisture backflow into the pump.
The 4.7L 2UZ-FE V8 used in later 4th-generation 4Runners is known for secondary air injection system failures involving the air pump and switching valves. When the system sticks or fails electrically, the truck may illuminate the check engine light and enter reduced-power or limp mode. This problem is widely documented across Toyota V8 trucks and SUVs of the era and can be very expensive when repaired with OEM components.
Common Symptoms
- check engine light
- reduced power or limp mode
- poor acceleration
- cold-start noise from air pump area
- traction and VSC lights illuminated with CEL
How to Fix
Scan for stored air injection codes and verify pump operation, valve movement, and moisture intrusion in the system. Repair usually requires replacing one or both air pumps and/or switching valves, plus related hoses or control components. Some owners use aftermarket bypass modules for off-road or out-of-warranty vehicles, but emissions legality varies by location.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Toyota 17600-0F010 secondary-air pump assembly
pump branch only when command, power, pressure and debris inspection confirm failure Fitment/availability: 2005-2009 Toyota 4Runner 4.7L 2UZ-FE bulletin branch; broader catalog fitment does not justify use without code-directed pump test…
- Genuine Toyota 25710-50022 secondary-air switching/check valve
main switching-valve branch only after the bulletin test identifies valve failure or debris damage Fitment/availability: 2005-2009 Toyota 4Runner 4.7L 2UZ-FE bulletin branch; supersedes 25710-50020 and 25710-50021 Fitment/availability: s…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
The 1GR-FE's secondary air injection system, used to reduce cold-start emissions, is prone to failure. Water/condensation intrusion corrodes the air pump and air switching valves, or a broken plastic impeller sheds debris into the system, triggering the check engine light and often limp mode. It is most common in cold and wet climates and can strand the vehicle in reduced-power mode.
Common Symptoms
- Check engine light
- Reduced power / limp mode
- Loud pump noise at cold start
- Warning lights (VSC/traction) illuminated together
How to Fix
Toyota's TSB requires replacing the air injection pump AND both air switching valves together (the factory fix is expensive). Many owners instead install a plug-and-play SAIS bypass/delete kit (e.g., Hewitt Technologies) to permanently eliminate the failure-prone components where emissions inspection allows.
Sources for this issue (4)
The secondary air injection (AI) system on the 100-series Land Cruiser (1998-2007) with the 2UZ-FE 4.7L V8 is a notorious failure point, identical to the issue on the Sequoia and Tundra of the same era. The electric AI pump, air switching valves (ASV), and exhaust manifold check valves all fail. The aluminum check valves in the exhaust manifolds corrode and seize, the ASV sticks from carbon buildup, and the pump motor eventually burns out. This system is responsible for the most common check engine light on 100-series Land Cruisers.
Common Symptoms
- Check engine light with air injection codes
- Loud whirring from AI pump on cold start
- AI pump not running on cold start (silence where there should be noise)
- Multiple emissions-related fault codes
- Failed emissions inspection
How to Fix
The complete repair involves replacing the AI pump ($300-$500), both ASV valves ($200-$400 each), and both exhaust manifold check valves ($100-$200 each). Total dealer cost: $1,500-$3,000. Many Land Cruiser owners in non-emissions states delete the entire AI system and install an ECU tune to suppress the codes ($300-$500 for the tune). In emissions states, the full repair is required. A common partial fix is to replace just the check valves and ASV, leaving the pump in place — the pump usually fails last.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Toyota 17600-0F010 genuine secondary-air pump assembly
bulletin-specified pump replacement after the covered DTC diagnostic path confirms the condition Fitment/availability: VIN-confirmed 2005-2007 Land Cruiser 2UZ-FE; T-SB-0230-12 repair authority is limited to applicable 2006-2007 vehicles…
- Toyota 25710-50022 genuine secondary-air control/check valve
replace only when inspection under T-SB-0230-12 shows debris damage to this valve Fitment/availability: VIN-confirmed 2005-2007 Land Cruiser 2UZ-FE; current valve replaces 25710-50020 and 25710-50021 Fitment/availability: Live direct pro…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipJoin IH8MUD.com — the definitive Land Cruiser forum. The AI system delete with ECU tune is thoroughly documented there with step-by-step instructions and recommended tuners.
Sources for this issue (1)
P0418 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0418 mean on a Toyota?
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. On Toyota it is documented across 6 models: Tundra, Sequoia, 4Runner, FJ Cruiser, Land Cruiser, Tacoma.
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 on a Toyota?
Published repair estimates on Toyota range from $100 to $4,000 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0418 on a different make?
View P0418 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.