OBD-II Code P2401 — What It Means & How to Fix It

What it means

The EVAP system uses a small pump to test for fuel vapor leaks, and P2401 means the ECM detected a low voltage in that pump's control circuit.
This is typically caused by a short to ground in the wiring.
Like most EVAP codes, this won't affect how your car drives, but the check engine light will stay on until it's repaired.

Affected Models

All vehicles 1996+ with EVAP leak detection pump
Common in Subaru vehicles
Common in some Nissan models
Common in some European vehicles with active EVAP testing

Common Causes

Short to ground in the pump control signal wire
Internal short in the leak detection pump motor
Damaged wiring rubbing against a metal ground surface
Corroded pump connector causing a low-resistance path to ground
Failed ECM output for the pump circuit

How to Fix It

Inspect the pump wiring harness for any areas rubbing on the chassis.

Wires chafing on sheet metal or frame rails are the most common cause of shorts to ground in EVAP circuits.
Disconnect the pump connector and check if the code clears — isolates the fault.

If the low-circuit code goes away with the pump disconnected, the short is inside the pump motor, not the wiring.
Test the control wire for shorts to ground with the pump unplugged.

Set your multimeter to resistance and measure between the signal wire and chassis ground — near-zero ohms confirms a wire short.
Measure pump motor resistance — a very low reading confirms an internal short.

Normal pump motor resistance is typically 20–40 ohms; a reading near zero means the motor windings are shorted.
Repair any shorted wiring, or replace the pump if it has an internal fault.

After the repair, clear the code and complete a full EVAP drive cycle to confirm the pump circuit tests normal.

When to Call a Professional

If disconnecting the pump and testing the harness doesn't isolate the short, have a mechanic trace the circuit with a wiring diagram.
Diagnosis involves systematically testing each segment of the harness to pinpoint where the short to ground occurs.
Expect $80–$130 for diagnosis; wiring repairs and pump replacement typically cost $50–$200 total.

Frequently Asked Questions

Will P2401 fail a smog test?

Yes.
Any active check engine light will fail an emissions inspection.
Get this repaired before your test date.

How do I find a short to ground in the wiring?

Disconnect the pump, then use a multimeter set to resistance.
Measure between the signal wire and a chassis ground.
A reading near zero ohms means there's a short.

Is P2401 expensive to fix?

Usually not.
Wiring repairs and a replacement pump are affordable.
Total cost is typically $50–$200 depending on labor rates.