Evaporative Emission System Leak Detection Pump Control Circuit Low
Diagnostic trouble code P2401 indicates that the powertrain control module (PCM) has detected a low voltage condition in the control circuit of the evaporative emission (EVAP) system leak detection pump. This typically means the circuit is shorted to ground or has an open connection, preventing the pump from operating correctly to test the EVAP system for leaks.
This code does not affect the drivability or safety of the vehicle. 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
- Failure to pass an emissions inspection
- Possible faint fuel odor near the vehicle
- No noticeable drivability issues
- EVAP system monitor shows 'incomplete' or 'not ready'
Likely causes
- Faulty EVAP leak detection pump
- Corroded or damaged connector at the leak detection pump
- Wiring harness shorted to ground or open in the pump control circuit
- Blown fuse providing power to the leak detection pump circuit
- Faulty powertrain control module (PCM) (rare)
What to check before replacing parts
Scan for additional codes and check the EVAP system fuse.
Look for: A blown fuse indicates a short circuit that needs to be traced. Other EVAP codes may help pinpoint a shared power or ground issue.
Visually inspect the wiring harness and connector at the EVAP leak detection pump.
Look for: Look for frayed wires, melted insulation, or severe corrosion inside the connector pins that could cause an open or short to ground.
Test for voltage at the leak detection pump connector with the key on (or during a bi-directional command).
Look for: If battery voltage is not present when commanded, there is an open circuit or short to ground in the wiring between the PCM/relay and the pump.
Check the ground circuit for the leak detection pump.
Look for: Using a multimeter, verify continuity to a known good ground. High resistance indicates a poor ground connection.
Test the internal resistance of the EVAP leak detection pump.
Look for: Compare the measured resistance across the pump terminals to the manufacturer's specifications. An out-of-spec reading (often an open or shorted coil) means the pump has failed internally.
This page explains the generic P2401 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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