P2403: Evaporative Emission System Leak Detection Pump Sense Circuit Open
What to do
The car drives normally. The pump may still run, but the module cannot read the result, so the leak test cannot complete — which shows up as an incomplete monitor at an emissions test rather than as a leak. Ask for the connector to be inspected before the pump is replaced.
What this code means
An open circuit in the sense line through which the module monitors the leak detection pump.
The control and sense distinction is the same one set out for NOx sensor heaters at P2208, and it does the same work here. Control is the output that runs the pump. Sense is the input that reports what the pump is achieving — how far its diaphragm travels, or how its current draw behaves, which is the measurement the whole leak test rests on. Running the pump is not the test; watching it is.
So losing the sense circuit does not stop the pump, it stops the test from meaning anything. The module cannot distinguish a sealed system from a leaking one and reports that it could not evaluate rather than that it found a leak — which is why this presents as an incomplete monitor rather than a leak code.
Likely causes
Start here
- Open circuit in sensor wiring · moderate
- Corroded or loose connector · easy
Less common
- Faulty EVAP leak detection pump · moderate
- Damaged wiring harness · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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