P2439
Secondary Air Injection System Air Flow/Pressure Sensor Circuit Intermittent/Erratic (Bank 2)
- Severity
- Low
- Driving
- Drivable — book it in
The secondary air flow or pressure sensor signal on bank 2 is erratic or dropping out. Because the system only runs briefly on a cold start, an intermittent fault here can take many days to catch - it can only appear during that one short window per journey.
Possible causes
- CommonLoose, corroded or backed-out connector pin
- CommonChafed or heat-damaged wiring near the exhaust
- CommonWater ingress into the connector
- PossibleFailing sensor
- PossiblePartially blocked sensing hose
What you might notice
- Check engine light appearing occasionally, often after a cold night
- Failed emissions test
- Usually no symptom the driver notices
What to check, in order
- Expect this to take several cold starts to reproduce. The system runs for about a minute a day, so patience is part of the diagnosis.
- Note whether it correlates with wet or cold weather, which points at the connector.
- Wiggle-test the harness with the live data screen showing the sensor reading.
- Inspect the connector for a backed-out pin and for water.
- Check the harness for heat damage where it runs near the exhaust.
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