P0412 on Toyota
Secondary Air Injection System Switching Valve A Circuit
P0412 on Toyota vehicles indicates secondary air injection system switching valve a circuit. Au7o has documented this code across 4 Toyota models — most commonly on 4Runner, Sequoia, Tacoma. This emissions code refers to a fault in the secondary air injection (AIR) system's switching valve 'A' circuit. The secondary air injection system pumps fresh air into the exhaust right after a cold start to help the catalytic converter heat up and burn off pollutants faster; the switching valve directs that air flow. The computer sets this code when the electrical control of valve A is open, shorted, or otherwise out of range. It generally affects only cold-start emissions, so you may not notice a drivability change, but it will fail emissions testing. Typical repair costs on Toyota range from $100 to $4,000, depending on the specific model and root cause.
Common Causes of P0412
- •Faulty secondary air switching/control valve
- •Open, shorted, or corroded valve wiring/connector
- •Blown fuse or faulty relay for the AIR system
- •Failed secondary air injection pump
- •Stuck or carbon-clogged air valve
- •Vacuum supply leak to the control valve
- •Faulty engine control module (PCM) — rare
P0412 on Toyota by Model
Toyota 4Runner(1 issue)
- Secondary Air Injection Pump/Valve Failure Triggering Limp Mode on 4.7L V82005-2009
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.
Toyota Sequoia(2 issues)
- Secondary Air Injection System Failure (2UZ-FE)2001-2009
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.
- Secondary Air Injection Pump Failure (3UR-FE/i-FORCE)2008-2019
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.
Toyota Tacoma(1 issue)
- Secondary Air Injection Pump and Switching Valve Failure on 4.0L V62005-2011
Tacomas with the 1GR-FE 4.0L V6 are known for failures of the secondary air injection system, including the air pump and switching valves. Moisture intrusion and valve sticking can trigger check-engine lights and force the truck into reduced-power or limp mode. Owners frequently report sudden loss of acceleration along with expensive dealer repair estimates because the intake manifold often must be removed to access components.
Toyota Tundra(1 issue)
- Secondary Air Injection Pump Failure2005-2013
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.
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View P0412 across all makes →Frequently Asked Questions
What does P0412 mean on Toyota?▼
P0412 stands for "Secondary Air Injection System Switching Valve A Circuit." This emissions code refers to a fault in the secondary air injection (AIR) system's switching valve 'A' circuit. The secondary air injection system pumps fresh air into the exhaust right after a cold start to help the catalytic converter heat up and burn off pollutants faster; the switching valve directs that air flow. The computer sets this code when the electrical control of valve A is open, shorted, or otherwise out of range. It generally affects only cold-start emissions, so you may not notice a drivability change, but it will fail emissions testing. On Toyota specifically, this code is documented across 4 models.
What causes P0412 on Toyota vehicles?▼
Common causes on Toyota: Faulty secondary air switching/control valve, Open, shorted, or corroded valve wiring/connector, Blown fuse or faulty relay for the AIR system, Failed secondary air injection pump, Stuck or carbon-clogged air valve. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0412 on a Toyota?▼
Repair costs on Toyota range from $100 to $4,000, depending on the specific model and root cause.
Which Toyota models have P0412 documented?▼
Au7o has documented P0412 on 4 Toyota models: 4Runner, Sequoia, Tacoma, Tundra.