What it means
The reductant purge control valve B control circuit voltage is above the expected range. This indicates an electrical fault, not necessarily a short to supply.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Reductant purge control valve B is electrically operated to clear AdBlue/DEF from parts of the system at shutdown. P24DE sets when the control module sees the valve B control circuit above its expected electrical range; it indicates a high circuit signal, but does not alone establish a short to the 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 or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Record freeze-frame data and check related reductant, valve, and NOx codes before clearing anything.
- Inspect the valve B connector for corrosion, loose terminals, or wiring repairs that could connect the control circuit to a supply.
- Trace the control harness for pinched or chafed insulation near power wires and other likely contact points.
- Using the wiring diagram, test the control circuit for an unintended connection to supply as specified by the manufacturer.
- If the harness and connector are sound, test valve B and its control circuit against the manufacturer's specification.
Common fixes
- Correct a loose or corroded connection at valve B.
- Repair wiring where the control line is pinched or contacting a supply wire.
- Replace damaged connector terminals or insulation that allows a supply connection.
- Replace valve B if it fails the specified electrical test.
Can I keep driving?
The vehicle may remain driveable, but the valve may not purge correctly and the fault can lead to emissions warnings or a no-start countdown on some vehicles. Follow any countdown warning and arrange diagnosis promptly.
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.