P2403
Evaporative Emission System Leak Detection Pump Sense Circuit/Open
- Severity
- Low
- Driving
- No driving restriction
The circuit that tells the module what the leak detection pump is doing is open - a broken wire, a disconnected plug, or a failed sensing element. This is the feedback half of the pump: the module drives the pump on one circuit and watches the result on this one. Without it the module can run the pump but cannot interpret the test, so the leak check never completes.
Possible causes
- CommonCorroded or water-damaged connector at the pump
- CommonFailed sense switch or sensor inside the pump assembly
- CommonDamaged wiring on the underbody run
- PossiblePoor earth at the pump
- PossibleBlocked or kinked vapour line preventing the pump from building pressure
What you might notice
- Check engine light on
- Failed emissions test
- Occasionally a smell of fuel
- Usually nothing else - EVAP faults rarely affect how the car drives
What to check, in order
- Inspect the connector and its wiring before condemning the component. Everything in this system lives under the vehicle in the path of road salt and spray, and a corroded connector produces these codes far more often than a failed part does.
- Watch the sense signal on live data while commanding the pump. It should change state as the pump runs; one that never moves is the sense circuit, one that moves erratically is usually a connection.
- Check the vapour lines for kinks and blockages. A pump that cannot build pressure because the line is blocked reports the same thing as a failed sensor.
- Check the earth before replacing the pump assembly. These are usually sold as a complete unit and are not cheap.
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