P24BF: Evaporative Emission System Leak Detection Pump Switching Valve Control Circuit High

What it means

Same as P24BD with the control line shorted to supply. The evaporative system captures fuel vapor from the tank and purges it into intake; leaks or stuck purge valves leak hydrocarbons and cause emissions failures.

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 switching valve routes pump flow through the EVAP test path or reference path. P24BF sets when the control line is higher than expected, commonly because it is shorted to a power feed, so the module cannot control the valve normally.

Common causes

Most likely first.

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

Symptoms

• Check engine light on
• Possible smell of fuel near tank or engine bay
• Failed emissions inspection
• Loose-cap warning may appear

How to diagnose it

1. Save freeze-frame data and review related EVAP codes to establish whether the fault occurred during a switching-valve command.
2. Inspect the valve connector and harness for pinched wiring, melted insulation, corrosion, or contact with a power feed.
3. Check connector terminals for looseness or corrosion that could disrupt the control circuit.
4. Use the wiring diagram and manufacturer's procedure to test the control wire for a short to supply and verify its continuity.
5. If wiring checks pass, test the valve and module output against the manufacturer's specification.

Common fixes

• Repair a control wire shorted to a power feed.
• Replace wiring pinched or melted against a power source.
• Repair corroded or loose valve connector terminals.
• Replace the switching valve if it fails testing.

Can I keep driving?

Driving is generally possible, but the EVAP system may be unable to run its leak check, which can lead to an emissions test failure. Have a persistent fuel smell checked promptly.