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DTC codes / P24xx · Auxiliary emission controls / P2400

P2400Evaporative Emission System Leak Detection Pump Control Circuit/Open

P2400 indicates that the engine computer has detected an open circuit or loss of continuity in the control circuit for the evaporative emission leak detection pump. The computer commands the pump to run during an evap system self-test but sees no expected voltage or current response on the control wire, so it flags the circuit as open.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • A slight fuel odor may be present if the leak detection pump cannot pressurize the system.
  • The evaporative emission monitor will not complete, causing an emissions test failure.
  • In some vehicles, a message such as 'Check Fuel Cap' or 'Evap System Leak' may appear.
  • Rough idle or driveability issues are unlikely unless the fault is combined with other evap codes.

Common causes, most likely first

  1. Broken, chafed, or disconnected wire in the leak detection pump control circuit.
  2. Corroded or loose electrical connector at the leak detection pump or at the engine computer.
  3. Failed leak detection pump solenoid or pump motor winding (open internal circuit).
  4. Blown fuse or faulty relay that supplies power to the leak detection pump circuit.
  5. Engine computer driver circuit failure (rare but possible after other causes are ruled out).
  6. Aftermarket alarm or remote start wiring that has tapped into or damaged the evap circuit.

How to diagnose and fix it

  1. Verify battery voltage and inspect all fuses related to the evaporative emission system, replacing any blown fuse after checking for shorts.
  2. Visually inspect the leak detection pump connector and the engine computer connector for corrosion, pushed pins, or loose terminals; clean and reseat as needed.
  3. Disconnect the leak detection pump and use a multimeter to check for battery voltage on the power feed wire with the key on, and check the ground circuit for continuity to chassis ground.
  4. Check the control circuit between the pump and the engine computer for continuity and resistance; repair any open or high-resistance wire.
  5. Command the leak detection pump on with a scan tool and listen for pump operation; if the pump does not run, test the pump motor directly with fused battery power.
  6. If the control circuit and pump are good, substitute a known-good relay or test the computer driver output with an oscilloscope or test light.
  7. Clear the code and run the evap monitor to confirm the repair; verify no pending codes return.

When the pump is not the culprit

  • A common misdiagnosis is replacing the leak detection pump when the real fault is a corroded connector or a broken wire hidden inside the harness loom near the fuel tank.
  • The control circuit open may be caused by a failed relay that supplies power to the pump, not by the pump itself, so always check relay operation before condemning the pump.
  • Some vehicles use a combined leak detection pump and purge solenoid assembly; a fault in the shared ground can set P2400 along with purge-related codes.
  • Aftermarket remote starters or alarm systems that tap into the evap wiring are a frequent source of open circuits that set this code.
  • P2400 does not always mean the pump is dead; the computer may set it if the control wire is shorted to ground or to power, so check for both opens and shorts.

Can I keep driving with P2400?

The vehicle is safe to drive with P2400 because the fault only affects the evaporative emission system and does not impact engine performance or safety. However, you should avoid topping off the fuel tank and park away from strong ignition sources until the leak detection pump circuit is repaired, as the evap system may not be able to purge fuel vapors properly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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