What it means
The reductant purge control valve B control circuit voltage is below the expected range. This indicates an electrical fault, not necessarily a short to ground.
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. P24DD sets when the control module sees the valve B control circuit below its expected electrical range; that points to a low circuit signal and does not by itself prove a short to ground.
Common causes
Most likely first.
- Control line shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
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 for related valve, reductant, and NOx codes to see when the low signal was detected.
- Inspect the valve B connector for corrosion, moisture, loose fit, or damaged terminals that could add resistance.
- Trace the control wire for chafing or crushed insulation, including spots where it could contact ground.
- With the wiring diagram, measure the control circuit as directed by the manufacturer and check for unwanted continuity to ground.
- If the harness and connector test correctly, test valve B's electrical load and control response against the manufacturer's specification.
Common fixes
- Clean corroded valve B connector terminals and restore a secure connection.
- Repair chafed or grounded wiring in the valve B control circuit.
- Replace damaged connector terminals that cause excessive resistance.
- Replace valve B if its electrical load is outside the manufacturer's specification.
Can I keep driving?
The vehicle may still drive, but the purge valve may not function correctly and emissions warnings or a no-start countdown may follow. Have the circuit checked soon and heed any countdown shown by the vehicle.
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.