What it means
Same as P04AB 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
EVAP purge control valve B is a solenoid that controls vapor flow from the canister into the intake. P04AD sets when the module sees voltage on valve B's control circuit higher than expected, which can happen if the control wire is shorted to a supply source.
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
- Possible smell of fuel near tank or engine bay
- Failed emissions inspection
- Loose-cap warning may appear
How to diagnose it
- Check freeze-frame and EVAP live data to confirm the fault is associated with purge valve B and record when it occurs.
- Inspect valve B's connector and harness for pinched wiring, damaged insulation, corrosion, or terminals that have shifted.
- With the circuit isolated as specified by the service information, check whether valve B's control wire is shorted to a supply wire or power source.
- Inspect the valve B connector terminals and verify the control wire is not contacting an adjacent powered circuit.
- Test the valve B solenoid and module-side control circuit against the manufacturer's specification to distinguish a wiring short from a component fault.
Common fixes
- Repair the control wire where it has contacted a supply source.
- Replace damaged connector terminals and restore proper pin fit.
- Repair pinched insulation and reroute the harness away from powered wiring or sharp edges.
- Replace purge valve B if its electrical test shows an internal fault.
Can I keep driving?
If the engine runs normally, gentle driving is usually possible, but arrange repair soon and take a fuel smell seriously. The EVAP system may fail to control vapors, increasing emissions and risking an inspection failure.
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.