P24DBReductant Purge Control Valve B Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- After shut-down an SCR system empties its lines back into the tank so no fluid freezes in them; in Bosch's Denoxtronic 2.2 a 4/2-way valve in the supply module reverses the flow for this. Valve B is a second purge valve, for instance in layouts with two dosing branches. P24DB reports a drive circuit fault of valve B, mostly an interruption. No manufacturer documents P24DB publicly. GM documents the method only for valve A (P20A0) on its 6.6 L diesel: with the low-side driver off, an impedance above 200 kΩ between ECM pin and load for 3 s counts as open, Type A. CARB's heavy-duty rules require all electrical SCR components to be monitored. Shorts are split off as P24DD and P24DE. A line that is not emptied risks frost damage.
- What you may notice
- Malfunction indicator lamp on
- DEF line not purged after shut-off, freezing risk in winter
- Likely causes
- LikelyBroken wire or unplugged connector to purge valve B
- PossibleOpen solenoid winding in valve B
- PossibleDEF-induced corrosion in the supply module connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.