Open or damaged wiring in the leak detection pump sense circuit, such as a broken wire or corroded connector.; Failed leak detection pump assembly, where the internal sense circuit is open.; Poor electrical connection at the pump or at the engine computer, including loose pins or water intrusion.; Blown fuse or faulty relay that supplies power to the leak detection pump circuit.; Faulty engine computer (rare) with an internal open circuit on the sense input.; Aftermarket or improper electrical accessories tapped into the circuit causing interference.

DTC codes / P24xx · Auxiliary emission controls / P2403

P2403Evaporative Emission System Leak Detection Pump Sense Circuit/Open

P2403 indicates that the engine computer has detected an open circuit or abnormal voltage on the evaporative emission (EVAP) system leak detection pump sense circuit. This circuit is used by the leak detection pump to report its position or readiness, and an open circuit prevents the computer from verifying that the pump is functioning during the EVAP leak test.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light (malfunction indicator lamp) with no other noticeable symptoms.
A slight fuel odor may be present if the EVAP system is not sealing properly, though this is not guaranteed.
In some vehicles, a pending code may set without turning on the light until a second fault is detected.
The remote start feature may be disabled on certain models as a precaution.
No drivability issues are typically observed because the fault affects only the emissions control system.
The EVAP monitor will not complete, which can cause an emissions test failure.

Common causes, most likely first

Open or damaged wiring in the leak detection pump sense circuit, such as a broken wire or corroded connector.
Failed leak detection pump assembly, where the internal sense circuit is open.
Poor electrical connection at the pump or at the engine computer, including loose pins or water intrusion.
Blown fuse or faulty relay that supplies power to the leak detection pump circuit.
Faulty engine computer (rare) with an internal open circuit on the sense input.
Aftermarket or improper electrical accessories tapped into the circuit causing interference.

How to diagnose and fix it

Verify the code with a scan tool and check for any related EVAP codes that might indicate a different root cause.
Inspect the leak detection pump connector and wiring for signs of damage, corrosion, or loose pins.
Check the fuse and relay that provide power to the leak detection pump circuit.
Measure resistance and voltage on the sense circuit according to the manufacturer's service information to confirm an open circuit.
If the wiring and connectors are good, test the leak detection pump itself by checking its internal resistance or swapping with a known-good unit.
Repair any damaged wiring or replace the faulty leak detection pump as needed.
Clear the code and perform a drive cycle to verify the repair and ensure the EVAP monitor completes.

Don't overlook the simple wiring checks

A common oversight is replacing the leak detection pump without first checking the wiring harness for chafing or rodent damage, which can mimic a failed pump.
The sense circuit is often a low-current signal path, so even slight corrosion at a connector can cause an open circuit that sets P2403.
On some vehicles, the leak detection pump is part of the fuel tank assembly, making replacement expensive; always confirm the pump is faulty before replacement.
P2403 can be set by a faulty fuel cap if the cap seal is compromised, though this is less common than a wiring issue.
A weak battery or charging system problem can cause erratic signals on the sense circuit and set this code intermittently.

Can I keep driving with P2403?

The vehicle is safe to drive with P2403 because it only affects the emissions control system and does not impact engine performance. However, you should avoid ignoring the code, as it will prevent the EVAP monitor from completing and may cause an emissions test failure. Have the fault diagnosed and repaired at your earliest convenience.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.