P2405 indicates the powertrain control module (PCM) has detected a low voltage signal on the sense circuit of the evaporative emission (EVAP) leak detection pump. This pump is used to pressurize the EVAP system during self-diagnostic leak tests, and the sense circuit tells the PCM whether the pump is cycling correctly. The fault is logged when the feedback signal does not match what the PCM expects during the test.
The pump's internal motor or position sensor is the most common failure point. Brush wear, moisture intrusion, and internal corrosion are typical, especially on higher-mileage vehicles.
The pump is often located near the fuel tank or under the vehicle, where connectors are exposed to road salt, water, and physical damage that can produce a low-voltage reading on the sense circuit.
A cracked, collapsed, or disconnected hose can prevent the pump from building expected pressure, causing the sense signal to read low during the test.
A broken wire or a short between the sense line and chassis ground pulls the signal low. This is distinct from a bad connector and must be traced with a wiring diagram.
Some systems use a changeover or cutoff valve that must open for the pump to operate correctly. A stuck-closed valve will keep the sense circuit in its low state.
In uncommon cases the PCM's internal driver or reference circuit for the LDP sense line is faulty. This should only be considered after the pump, wiring, hoses, and valves have all been ruled out.
Yes, in most cases. This code is emissions-related and does not typically affect engine performance, fuel economy significantly, or safety. The vehicle can usually be driven normally until repairs are convenient.
Almost certainly not. P2405 will set the check engine light and typically prevents the EVAP readiness monitor from completing, which is required for inspection in most jurisdictions.
No. Despite what some online sources suggest, replacing the engine computer is almost never the correct fix. The leak detection pump, its wiring, and its hoses are responsible for the great majority of P2405 cases, and the PCM should only be suspected after those components have been thoroughly tested.
Clearing the code is reasonable as a confirmation step, but if the underlying mechanical or electrical fault is not repaired, the code will return after the EVAP self-test runs, which may take one or more drive cycles.