What it means
The second EVAP purge control valve (B) - used on systems with a divided purge path or on twin-bank engines - shows an open control circuit. The ECU cannot drive the valve, so vapor cannot be purged through this stage; tank pressure may rise and emissions diagnostics fail.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
EVAP purge control valve B is a solenoid that lets fuel vapor travel from the charcoal canister toward the engine for burning. P04AB sets when the control module detects an open electrical path in valve B's control circuit, so it cannot operate that purge stage.
Common causes
Most likely first.
- Open in harness or connector
- Solenoid winding open
- Pin pushed back out of connector body
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
- Use freeze-frame data and EVAP live data to confirm P04AB is current and note whether purge valve B is being commanded.
- Inspect valve B's connector for a loose plug, corrosion, moisture, or a terminal pushed back in the connector body.
- Trace the valve B harness for breaks or chafing, paying attention to bends and clips near the valve.
- Check continuity through the valve B solenoid winding against the manufacturer's specification to identify an open winding.
- With the circuit safely isolated as directed by the service information, check the control wiring for an open between valve B and the module.
Common fixes
- Reconnect valve B's loose plug and secure its harness.
- Repair an open or damaged section of the valve B control wire.
- Replace corroded or pushed-back connector terminals.
- Replace purge control valve B if its solenoid winding is open.
Can I keep driving?
The vehicle will often remain drivable, but avoid ignoring a persistent fuel-vapor smell, especially near the tank or engine bay. The EVAP system may not control vapors correctly and the vehicle may fail an emissions inspection.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.