Open circuit, chafed or corroded wiring between the control unit and the refuelling vapour control valve; Poor connection at the valve connector, such as a loose, corroded or pushed-out terminal; Failed valve with an open internal coil; Blown fuse or a fault in the power or earth supply to the valve circuit; Wiring damage from underbody impact, water ingress or previous repair work near the tank; Fault inside the controlling module's output driver; Outdated control unit software where the manufacturer has documented it as a cause for the model.

P04B0

Refueling Vapor Control Valve Circuit/Open.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
B0: FaultThe specific fault in that area

What it means

P04B0 means the control unit has detected an open circuit in the refuelling vapour control valve circuit. This valve manages fuel vapour flow from the tank during refuelling, and is typically found on sealed or pressurised fuel tank systems. The control unit sets the code when the valve's electrical feedback or current shows no continuity, such as a broken wire, a poor connection or a failed valve coil. Layout and operation vary by model and engine.

Symptoms

Malfunction indicator lamp on
Difficulty refuelling, such as the pump clicking off repeatedly
Fuel filler release slow or not working on models with a sealed tank
Fuel smell near the filler or tank
Evaporative emissions or readiness monitors not completing
Fuel tank pressure behaving unusually

Possible causes

Open circuit, chafed or corroded wiring between the control unit and the refuelling vapour control valvelikely
Poor connection at the valve connector, such as a loose, corroded or pushed-out terminallikely
Failed valve with an open internal coillikely
Blown fuse or a fault in the power or earth supply to the valve circuitpossible
Wiring damage from underbody impact, water ingress or previous repair work near the tankpossible
Fault inside the controlling module's output driverrare
Outdated control unit software where the manufacturer has documented it as a cause for the modelrare

How to diagnose

Read all stored and pending codes and the freeze frame data to see when the fault set and whether other evaporative or fuel tank pressure codes are present.
Check the manufacturer's information for the model to find the valve location and circuit layout, as these vary by vehicle.
Visually inspect the valve, its connector and the wiring for damage, corrosion, water ingress, chafing and loose or pushed-out terminals.
Check the relevant fuse and confirm the supply voltage and earth at the valve connector with the circuit live.
Measure the valve coil resistance and compare it with the specification for the model.
With the connector disconnected, test the wiring to the control unit for continuity, shorts to earth and shorts to supply.
Use a bidirectional scan tool function, if available, to command the valve and check for a response or click.
Clear the code after repair and retest, confirming it does not return and that the monitors complete.

How to fix

Repair or replace damaged wiring and secure it clear of sharp edges and heat sources.
Clean, repair or replace the corroded or damaged connector and terminals.
Replace the refuelling vapour control valve if the coil is open or it fails the command test.
Replace the blown fuse after finding and fixing the cause of the failure.
Update the control unit software only if the manufacturer lists it as a fix for this fault on the vehicle.
Replace or repair the control unit only after the wiring and valve have been proven good and the manufacturer's diagnostics point to it.

Can I keep driving?

Low severity

The car can normally be driven and the fault is unlikely to cause immediate damage. Book it in soon, because refuelling may be affected and fuel vapour could escape if the system is not working properly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.