P2405: EVAP System Leak Detection Pump Sense Circuit Low

What it means

The control module detects a low signal in the EVAP leak detection pump sense circuit. This is an electrical fault; the code alone does not establish the cause.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The leak detection pump sense circuit reports pump feedback to the control module during an EVAP leak check. This code sets when that sense signal is lower than expected, which can result from a short to ground, damaged wiring, or a poor connection.

Common causes

Most likely first.

1. Sense line shorted to ground
2. Connector pins corroded - high contact resistance
3. Harness chafing through insulation

Symptoms

• Check engine light on

How to diagnose it

1. Record freeze-frame data and check whether the low sense reading appears when the leak detection pump is commanded.
2. Inspect the pump sense wire and connector for chafing, exposed conductor, corrosion, or loose terminals.
3. Check the sense signal at the pump and module connectors during the manufacturer's EVAP test procedure.
4. With the circuit isolated as specified by the manufacturer, test the sense wire for a short to ground and check connector continuity.
5. If wiring and connections pass, test the pump's sense output against the manufacturer's specification.

Common fixes

• Clean corroded terminals or secure a loose pump sense connector.
• Repair chafed sense-wire insulation that is grounding the circuit.
• Repair a damaged or high-resistance sense-circuit connection.
• Replace the leak detection pump if testing confirms its sense output is faulty.

Can I keep driving?

The low sense signal usually does not affect engine operation, so driving is generally possible. The EVAP system may be unable to verify its leak test, increasing emissions and potentially preventing an emissions inspection from passing.