Evaporative Emission System Leak Detection Pump Sense Circuit Low
Diagnostic trouble code P2405 indicates that the powertrain control module (PCM) has detected a low voltage condition in the evaporative emission (EVAP) system leak detection pump sense circuit. This typically means the signal voltage from the leak detection pump has fallen below the manufacturer's specified threshold, indicating a potential circuit fault or pump failure.
This code primarily affects the vehicle's emissions system and will not cause drivability issues. However, it will cause the vehicle to fail an emissions test and should be repaired to ensure proper EVAP system monitoring.
Common symptoms
- Illuminated Check Engine Light (MIL)
- Failed emissions test
- Slight fuel odor near the vehicle (rare)
- No noticeable drivability symptoms
- Incomplete EVAP system readiness monitor
Likely causes
- Faulty EVAP leak detection pump
- Corroded or damaged wiring in the leak detection pump circuit
- Loose or poor electrical connection at the leak detection pump
- Short to ground in the leak detection pump sense 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 frayed wires, corrosion, bent pins, or signs of moisture intrusion that could cause a low voltage signal or short to ground.
Check the battery voltage and ground connections to the leak detection pump.
Look for: Using a multimeter, verify that the pump is receiving the correct reference voltage and has a solid ground. A reading below specification indicates a wiring or supply issue.
Test the leak detection pump sense circuit for a short to ground.
Look for: Disconnect the pump and the PCM, then measure resistance between the sense wire and ground. Continuity indicates a short to ground in the wiring harness.
Test the internal resistance of the EVAP leak detection pump.
Look for: Measure the resistance across the pump's terminals and compare it to the manufacturer's specifications. An out-of-spec reading indicates an internal failure of the pump.
Command the leak detection pump on using a bi-directional scan tool.
Look for: Monitor the sense circuit voltage on the scan tool data stream. If the voltage remains low despite the command and wiring is intact, the pump or PCM may be at fault.
This page explains the generic P2405 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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