P04B1

Symptoms

• Check Engine Light Is On
• Strong smell of gasoline during and after refueling
• Fuel vapor escapes through the tank neck when refueling.
• Unstable priming gun (gun may fire too often)
• Possible increase in pressure in the fuel tank
• Deterioration of the vehicle's environmental performance

Causes

• Broken wire in the valve control circuit
• Oxidized or poorly connected valve connector
• Faulty valve solenoid (winding break)
• Damage to wiring caused by fuel or moisture
• Blown control circuit fuse
• Malfunctioning EVAP control module or ECU (rare)

How to Fix

1. Check the fuses of the EVAP circuit and the vapor control valve when refueling.
2. Find the location of the valve (usually near the fuel tank or neck)
3. Inspect the valve connector: oxidation, deformation, reliability of fixation
4. Measure the resistance of the valve solenoid (normal: 20–60 ohms)
5. Check the supply voltage and signal wire upon control command
6. Inspect the wiring harness from the ECU to the valve for damage.
7. Replace the valve if the solenoid is internally broken
8. After replacement, check the EVAP system and reset the codes

Related codes

Error P04B1 by Vehicle Brand