Evaporative Emission System Leak Detection Pump Sense Circuit Range/Performance
The powertrain control module (PCM) monitors the evaporative emission (EVAP) leak detection pump sense circuit to ensure it operates within expected parameters during system self-testing. This code is set when the PCM detects that the voltage signal from the leak detection pump sense circuit is out of its normal range or behaving illogically.
This is an emissions-related issue that will not affect the vehicle's drivability or safety. However, it will cause the vehicle to fail an emissions inspection and should be repaired to ensure proper EVAP system function.
Common symptoms
- Illuminated Check Engine Light
- Failed emissions inspection
- Faint smell of fuel vapor (in some cases)
- No noticeable drivability symptoms
- Stored diagnostic trouble code (DTC)
Likely causes
- Faulty EVAP leak detection pump (LDP)
- Cracked, disconnected, or blocked vacuum lines to the LDP
- Corroded or damaged wiring and connectors in the LDP sense circuit
- Faulty EVAP purge control valve
- Restricted EVAP canister or vent lines
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Visually inspect the wiring harness and connectors at the leak detection pump.
Look for: Look for frayed wires, corrosion, bent pins, or loose connections that could cause high resistance or an open circuit.
Inspect all vacuum lines connected to the leak detection pump and intake manifold.
Look for: Check for cracks, dry rot, disconnections, or blockages that would prevent the pump from generating or reading proper vacuum.
Use a scan tool to monitor the leak detection pump sense circuit voltage while commanding the pump on.
Look for: The voltage should change smoothly and stay within the manufacturer's specified range; erratic or static readings indicate a sensor or wiring fault.
Test the leak detection pump internal resistance using a digital multimeter.
Look for: Compare the resistance reading across the pump's terminals to the factory specification; an out-of-limits reading means the pump has failed internally.
Perform a smoke test on the EVAP system.
Look for: Look for smoke escaping from the leak detection pump housing, EVAP canister, or associated hoses, which indicates a physical leak affecting pump performance.
This page explains the generic P2404 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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