Evaporative Emission System Leak Detection Pump Sense Circuit High
Diagnostic trouble code P2406 indicates that the powertrain control module (PCM) has detected a high voltage condition in the sense circuit of the evaporative emission (EVAP) system leak detection pump. This typically means the voltage signal from the leak detection pump sensor is exceeding the maximum expected threshold, pointing to an electrical or component fault.
This code primarily affects the vehicle's emissions system and will not cause drivability issues. It is safe to drive, but should be repaired to pass emissions testing and ensure the EVAP system functions correctly.
Common symptoms
- Illuminated Check Engine Light
- Failed emissions test
- Slight decrease in fuel economy (rare)
- Fuel odor near the vehicle (rare)
- No noticeable drivability symptoms
Likely causes
- Faulty EVAP leak detection pump
- Short to voltage in the leak detection pump sense circuit wiring
- Corroded or damaged connector at the leak detection pump
- Open circuit in the leak detection pump ground or signal wire
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Scan for other EVAP codes and clear the system to see if P2406 returns.
Look for: If the code returns immediately, it indicates a hard electrical fault rather than an intermittent issue.
Visually inspect the wiring harness and connector at the EVAP leak detection pump.
Look for: Look for chafed wires, broken insulation, corrosion in the connector pins, or signs of moisture intrusion.
Test the voltage at the leak detection pump sense circuit with a digital multimeter.
Look for: With the key on, check if the voltage on the sense wire is higher than the manufacturer's specification (often 5V or battery voltage), indicating a short to power.
Check the ground circuit for the leak detection pump.
Look for: A high resistance or open ground can cause the sense circuit voltage to read high. Resistance should be near zero ohms to a good chassis ground.
Test the leak detection pump component itself according to the manufacturer's service manual.
Look for: If the wiring is intact but the internal resistance of the pump's sensor is out of specification, the pump assembly is faulty and requires replacement.
This page explains the generic P2406 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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