P2400: EVAP leak-detection pump control circuit is diagnosed open

P2400 is the electrical open-circuit diagnosis for the leak-detection pump in the reviewed GM conventional vented EVAP system with a fuel tank zone module. It does not report a measured vapor leak size or directly establish that the pump cannot create vacuum.

The driver is checked while off

The controller evaluates its low-side driver voltage with the output powered off. A response outside the accepted range indicates an open circuit. The source's controller design specification is impedance above 200 kilohms between the output and controller ground.

That figure describes the detection design; it is not a direction to resistance-test an energized fuel-vapor-system circuit. Nor can a generic EVAP leak test substitute for evaluating this electrical path.

Availability and persistence

The diagnostic requires supply above 11 V and no active EVAP-device communication fault. It uses 50 failed samples out of 63, taking a sample every 250 milliseconds. A single observation or a test conducted with unavailable module communication may not address the stored result.

Confirm the system actually uses the documented pump and fuel tank zone module, then follow its circuit procedure. If the pump can operate during a separate command, preserve that evidence without assuming it proves the off-state electrical check passed.

After repair, verify the control circuit's permitted off-state response and monitor completion without recurrence. The source specifies Type B, two-trip behavior and does not identify a disconnected connector, damaged wire or required pump replacement.

Source and applicability

The documented control architecture and calibration require confirmation for the vehicle being diagnosed. GM diagnostic table, PDF page 646.