Powertrain, generic (extended)

P2DD4 Control Pilot Charging Switch B Stuck On

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2DD4 describes the reverse case: switch B remains closed against the module's command to open, and the pilot goes on asking for energy at about 6 V although charging should have ended or paused. Welded or sticking contacts, a driver stage shorted on, or software that does not release the switch are all possible. For switch A, Mercedes-Benz traced the corresponding code P0CFE to the AC charger software and cured it by SCN coding, advising against swapping parts, so an update check comes first. No manufacturer documents P2DD4 publicly. CARB requires plug-in hybrids to monitor the on-board charger. Counterpart: P2DD3; circuit faults: P2DCE to P2DD1. Scheduled charging pauses may be ignored, or the session may end with an error message instead of finishing normally.

Likely causes

Charger software not releasing the switch
Welded or sticking switch contacts
Driver stage permanently switched on

Symptoms

  • Charging does not end or pause as planned
  • Charging error message after the session

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€50–1,500
Time0.5–3 h

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

Parts involved

control pilot switch bwiring harnesson board charger

Related codes

P2DD3P2DCEP2DCFP2DD0P2DD1P0CFE

References: static.nhtsa.gov, en.wikipedia.org, law.cornell.edu.