When the vehicle initializes its automated cold-start self-test, the PCM commands the LDP to run. If the engine computer sends the signal but detects an absolute open voltage return on the sense line, the fault is instantaneously logged. Common Root Causes OBD II Error Code P2403 Solution - PartsAvatar.ca
: The car gets stuck in gear or refuses to engage a gear.
: While rare with a "circuit" code, if the system cannot properly manage vapors, you might notice a faint smell of gasoline around the vehicle. Root Causes Faulty Leak Detection Pump : The internal sensor or the pump motor itself has failed. Wiring Issues smart p2403.40h
: While still in the development phase, autonomous or self-driving vehicles represent the future of smart mobility. They use a complex array of sensors and artificial intelligence to navigate roads without human input.
: On compact platforms like the Smart Fortwo, the LDP is positioned beneath the vehicle body near the charcoal canister or rear wheel well arch. This exposes the electrical wiring harnesses directly to water, slush, and road salt. Over time, moisture gets past the weather-stripping seals, corroding the harness connector pins and cutting off the sense signal. : While rare with a "circuit" code, if
[ Fuel Tank ] ---> [ Charcoal Canister ] ---> [ Purge Valve ] ---> [ Engine Intake ] ^ | (Monitors Pressure/Vacuum) [ Leak Detection Pump (LDP) ] (Monitors for open/short circuits)
Because the transmission cannot guarantee safe gear engagement, the computer implements safety protocols. You will likely experience several of the following symptoms: They use a complex array of sensors and
In select older Smart models (such as the Fortwo 450 /451), generic OBD-II scanners occasionally misinterpret deep proprietary transmission module codes. On these platforms, severe transmission actuator or clutch binding issues sometimes trigger phantom cross-communication faults or display misleading module errors like P2403 on cheap scan tools. Diagnostic Step-by-Step
When the computer detects an —meaning it receives zero electrical feedback or a completely broken connection—it triggers the P2403.40h fault code. Core Specifications: P2403.40h Breakdown Component Parameter Technical Specification DTC Category Powertrain (P-Code) Auxiliary Emission Controls System Definition EVAP Leak Detection Pump Sense Circuit/Open Sub-Fault Code (.40h)
: Once the hardware fix is complete, use your OBD-II scanner to clear out the fault codes. Take the vehicle on an extended test drive that includes steady highway cruising to let the engine computer re-run its internal EVAP monitoring diagnostics and permanently clear the dashboard light.