Powertrain, generic (extended)

P2D75 Battery Charging System Negative Contactor D Control Circuit Low

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modeNo

P2D75 is stored when the drive line of negative charging contactor D reads low. No manufacturer documents P2D75 publicly. How serious this is depends on wiring: a GM patent shows the coil switch either on the supply side or on the ground side. If the module switches the ground side, a short to ground at that end bypasses the switch, so the coil can energise and minus contactor D can close although nothing was commanded; charging is then locked for safety. With supply-side switching the same short simply leaves the contactor open. CARB permits makers to combine open and short faults of an output under one code, so not every system sets a separate low code. Chafed wires and wet plugs are typical. P2D76 is the high case, P2D6E the plus side.

Likely causes

Drive wire of contactor D shorted to ground

Moisture in the contactor D connector

Output stage shorted inside the module

Symptoms

Charging locked
Contactor may click without a command
Fault worse in damp weather

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€100–1,500

Time1–5 h

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

Parts involved

bcs neg contactor dwiring harnessbms

References: patents.google.com, law.cornell.edu.