P2401: EVAP leak-detection pump output has a low-circuit fault

P2401 reports a short-to-ground signature in the leak-detection pump control circuit for the reviewed GM fuel-tank-zone-module EVAP system. Its circuit-low title concerns electrical behavior rather than measured fuel-tank pressure or leak size.

Why an off-state check matters

The low-side output driver is evaluated while powered off. Voltage outside the controller's accepted off-state range indicates the ground-short condition. The source lists less than 0.5 ohm between output and controller ground as the driver design specification.

A low reading during an intentionally grounded on command is not equivalent to an unwanted ground path during the monitored off state. This command distinction is more useful than treating any low voltage as evidence that the pump itself is defective.

Test prerequisites

Supply must exceed 11 V and the EVAP device communication fault must be absent. The decision requires 50 failures in 63 samples at 250-millisecond intervals. Preserve those conditions when investigating an intermittent result; a later static observation may not cover the same operating window.

Use the applicable electrical diagnosis to separate circuit, connected load and driver evidence. The impedance figure is not an instruction for live resistance testing, and the source does not publish a connector pinout.

Verification should establish correct off-state response and allow the enabled monitor to complete without recurrence. Type B, two-trip behavior is documented. P2401 alone does not prove a vapor leak, blocked vent or mandatory pump replacement.

Source and applicability

The documented control architecture and calibration require confirmation for the vehicle being diagnosed. GM diagnostic table, PDF page 647.