P2431 on Subaru
Secondary Air Injection System Air Flow/Pressure Sensor Circuit Range/Performance (Bank 1)
P2431 on Subaru vehicles indicates secondary air injection system air flow/pressure sensor circuit range/performance (bank 1). Au7o has documented this code across 1 Subaru model — most commonly on WRX. This code means the engine computer detected that the secondary air injection (SAI) system airflow or pressure sensor on Bank 1 is reading outside its expected range. The SAI system pumps fresh air into the exhaust during cold starts to help burn off excess hydrocarbons and reduce emissions while the catalyst warms up. An out-of-range sensor reading means the computer can't verify the system is delivering the correct amount of air. It mainly affects cold-start emissions and is not an immediate driving hazard, but should be repaired to pass inspections. Typical repair costs on Subaru range from $700 to $2,200, depending on the specific model and root cause.
Common Causes of P2431
- •Faulty secondary air injection pressure/flow sensor
- •Stuck or faulty secondary air injection pump
- •Clogged or leaking air injection passages/hoses
- •Faulty air switching/check valve
- •Wiring or connector fault at the sensor
- •Carbon buildup restricting airflow
P2431 on Subaru by Model
Subaru WRX(1 issue)
- Secondary Air Injection Pump and Switching Valve Failure Triggering CEL and Limp Mode2006-2014
Turbo EJ255/EJ257 WRX models equipped with the secondary air injection system commonly develop failures of the air pump, pressure sensor, or the air switching valves. Moisture intrusion and corrosion can cause the valves to stick or the pump to seize, which sets emissions faults and on many cars can reduce power or force a limp-home condition. Owners typically report a check-engine light shortly after cold start, often with rough cold operation or an audible pump noise before failure.
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What does P2431 mean on Subaru?▼
P2431 stands for "Secondary Air Injection System Air Flow/Pressure Sensor Circuit Range/Performance (Bank 1)." This code means the engine computer detected that the secondary air injection (SAI) system airflow or pressure sensor on Bank 1 is reading outside its expected range. The SAI system pumps fresh air into the exhaust during cold starts to help burn off excess hydrocarbons and reduce emissions while the catalyst warms up. An out-of-range sensor reading means the computer can't verify the system is delivering the correct amount of air. It mainly affects cold-start emissions and is not an immediate driving hazard, but should be repaired to pass inspections. On Subaru specifically, this code is documented across 1 model.
What causes P2431 on Subaru vehicles?▼
Common causes on Subaru: Faulty secondary air injection pressure/flow sensor, Stuck or faulty secondary air injection pump, Clogged or leaking air injection passages/hoses, Faulty air switching/check valve, Wiring or connector fault at the sensor. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P2431 on a Subaru?▼
Repair costs on Subaru range from $700 to $2,200, depending on the specific model and root cause.
Which Subaru models have P2431 documented?▼
Au7o has documented P2431 on 1 Subaru model: WRX.