P2404 is set when the powertrain control module (PCM) detects that the signal from the leak detection pump (LDP) sense circuit is outside its expected range or performance. This occurs during the EVAP system's self‑test, indicating a fault in the pump or its wiring rather than an external vapor leak. The code is primarily an emissions‑related concern and does not usually affect engine drivability.
The pump’s internal motor or sense circuitry can wear out, causing the voltage or frequency signal to fall outside the PCM’s expected range.
An open, short, corrosion, or poor ground in the LDP sense circuit can prevent the PCM from reading the correct signal.
If the tank pressure sensor provides an incorrect pressure reading, it can make the LDP sense circuit appear out of range.
A vent or purge valve that fails to open or close properly can create abnormal pressure in the EVAP system, affecting the LDP sense signal.
In very few cases, outdated or incorrect PCM software can misinterpret the LDP sense circuit, but this is far less common than component failures.
No, the PCM is rarely the cause. Most cases are due to a faulty leak detection pump or wiring/connector problems; the computer should be considered only after all other components are verified.
The vehicle will usually still drive, but the Check Engine Light will remain on and you may fail an emissions test. It is advisable to repair the issue before a test or if you notice a fuel odor.
In most vehicles the engine runs normally; drivability symptoms are uncommon, though a rough idle or stalling may be noticed in some cases.
Not always. The pump is a common cause, but a proper test of the pump, wiring, and related sensors should be performed before replacing any part.