Powertrain, generic (extended)

P24DD Reductant Purge Control Valve B Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P24DD means the control line of purge valve B shows too little voltage at a moment when it should be high. With the low-side switching that GM uses for valve A, this is checked while the driver is off: the line should then carry battery voltage through the coil, and a low reading indicates a short to ground between valve and controller, so the valve may sit energised permanently. No manufacturer documents P24DD publicly; The valve A counterpart, P20A2, appears in GM's diesel tables for the 6.6 L engine. CARB's heavy-duty rules require detection of such circuit faults on SCR actuators. Typical spots are chafed wires near the tank and a coil that shorts to its housing. The opposite case is P24DE, an interruption P24DB.

Likely causes

Control wire chafed to ground near tank or frame
Valve coil shorted to its housing
Water or DEF in the connector

Symptoms

  • Malfunction indicator lamp on
  • Valve may remain in purge position, dosing pressure not reached

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–1,500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant purge valve b

Related codes

P24DBP24DEP20A2

References: gsi.ext.gm.com, law.cornell.edu.