Evaporative Emission System Leak Detection Pump Sense Circuit/Open
Diagnostic trouble code P2403 indicates that the powertrain control module (PCM) has detected an open circuit or lack of voltage in the evaporative emission (EVAP) system leak detection pump sense circuit. The PCM sets this code when it does not receive the expected feedback signal from the leak detection pump, preventing the system from properly monitoring for fuel vapor leaks.
This code primarily affects the vehicle's emissions system and will not cause drivability issues or strand you. However, it will cause the vehicle to fail an emissions test and should be repaired to ensure proper EVAP system operation.
Common symptoms
- Illuminated Check Engine Light
- Failure to pass an emissions inspection
- Possible faint fuel odor near the vehicle
- No noticeable drivability issues
- EVAP system readiness monitor incomplete
Likely causes
- Faulty EVAP leak detection pump
- Damaged, corroded, or loose wiring in the leak detection pump sense circuit
- Poor electrical connection at the leak detection pump connector
- Blown fuse providing power to the leak detection pump circuit
- Faulty powertrain control module (PCM) (rare)
What to check before replacing parts
Visually inspect the wiring and connector at the EVAP leak detection pump.
Look for: Look for broken wires, corrosion, bent pins, or a disconnected harness that would cause an open circuit.
Check the fuse(s) related to the EVAP system and leak detection pump.
Look for: A blown fuse indicates a short circuit that needs to be addressed before replacing the fuse or pump.
Test for power and ground at the leak detection pump connector with the key on.
Look for: Using a multimeter, verify that the pump is receiving battery voltage and has a solid ground. Lack of voltage indicates a wiring or PCM issue.
Test the sense circuit wire for continuity between the pump connector and the PCM.
Look for: High resistance or an open circuit (infinite resistance) confirms a break in the wiring harness.
Test the leak detection pump internally for proper resistance.
Look for: Compare the pump's internal resistance to the manufacturer's specifications. An open circuit inside the pump means it must be replaced.
This page explains the generic P2403 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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