What it means
Same as P04B0 with the control line shorted to supply. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The refueling vapor control valve directs tank vapors to the canister during refueling. P04B2 sets when the module detects voltage on the valve control circuit higher than expected, which can indicate the control wire is shorted to a power supply.
Common causes
Most likely first.
- Control line shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Fuel vapors may escape during refueling
- Fuel odor around the filler area
- Refueling may be interrupted or difficult
How to diagnose it
- Review freeze-frame and EVAP data to verify the fault is tied to the refueling vapor valve circuit.
- Inspect the valve connector and harness near the tank and filler for pinched insulation, corrosion, loose terminals, or contact with powered wiring.
- With the circuit isolated as directed by the service information, check whether the valve control wire is shorted to a supply source.
- Check terminal fit and continuity along the control wire to locate damage or an unintended connection.
- Test the valve and module-side control circuit against the manufacturer's specification before condemning either component.
Common fixes
- Repair the control wire where it has contacted a supply source.
- Replace damaged or poorly fitting connector terminals.
- Repair pinched insulation and secure the harness clear of powered wires and sharp edges.
- Replace the refueling vapor valve if its electrical test shows an internal fault.
Can I keep driving?
If there is no fuel leak, cautious driving to a repair location is generally possible, but do not refuel if vapor escapes or filling becomes difficult. Escaping vapors can create a fire hazard and the emissions system may not pass 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.