P2406: EVAP System Leak Detection Pump Sense Circuit High

What it means

The control module detects a high 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 sends feedback to the control module during EVAP leak checks. This code sets when the feedback signal is higher than expected, which can result from a short to supply, damaged wiring, or a poor connection.

Common causes

Most likely first.

1. Sense line shorted to supply
2. Connector pins corroded - high contact resistance
3. Supply wire pinched against B+ source

Symptoms

• Check engine light on

How to diagnose it

1. Record freeze-frame data and check whether the high sense reading occurs when the leak detection pump is commanded.
2. Inspect the pump sense harness for pinched insulation, contact with a power source, or loose or corroded connector terminals.
3. Compare the sense signal at the pump and control 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 supply and check connector continuity.
5. If the wiring and connections pass, test the pump's sense output and receiving circuit against the manufacturer's specification.

Common fixes

• Clean or secure a loose or corroded pump sense connector.
• Repair pinched sense-wire insulation where it contacts a supply wire or source.
• Repair a confirmed short to supply or damaged sense-circuit connection.
• Replace the leak detection pump if testing confirms its sense output is faulty.

Can I keep driving?

The high sense signal usually does not affect engine operation, so driving is generally possible. The EVAP system may not complete its leak check, increasing emissions and potentially preventing an emissions inspection from passing.