P2431
Secondary Air Injection System Air Flow/Pressure Sensor Circuit Range/Performance (Bank 1)
- Severity
- Low
- Driving
- Drivable — book it in
The secondary air flow or pressure sensor on bank 1 is answering, but the value it reports is not plausible. Either the sensor is inaccurate, or the flow genuinely is wrong - and on an older engine the second is more likely, because the air passages carbon up.
Possible causes
- CommonCarbon blocking the air passages, so the flow genuinely is wrong
- CommonFailing or drifting sensor
- CommonBlocked or perished sensing hose
- PossibleWeak air pump
- PossibleCheck valve failed or partially blocked
- PossibleHigh resistance in the wiring skewing the reading
What you might notice
- Check engine light on
- Failed emissions test
- Pump sounding different from usual on a cold start
- Usually no symptom the driver notices
What to check, in order
- Test from a cold start and watch the sensor reading while the pump runs.
- Establish whether the flow is genuinely wrong before blaming the sensor. A blocked passage produces a perfectly accurate reading of a real problem.
- Check the sensing hose for blockage and perishing.
- Inspect the air passages into the exhaust manifold for carbon.
- Check the check valve on bank 1.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx