Powertrain, generic (extended)

P2D74 Battery Charging System Negative Contactor D Control Circuit Range/Performance

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modeNo

P2D74 says the coil circuit of minus charging contactor D answers commands in an unexpected way, although it is neither open nor shorted. No manufacturer documents P2D74 publicly, and no published GM table has a range test for charge contactor coils. One measure a GM patent proposes is timing: how quickly the coil current climbs to a set level after the driver switches on. A slow rise suggests extra resistance in the circuit or a changed coil. That patent runs its test at key-on or remotely by telematics. CARB asks for a functional check of monitored outputs where feasible. Typical are aged plugs, a degraded coil and a weak driver. P2D73 is the open, P2D75/P2D76 low and high, P2D6D the plus side.

Likely causes

Aged connector adding resistance to the coil circuit

Coil of minus contactor D with changed resistance or inductance

Output stage no longer delivering full current

Symptoms

Charging via contactor D stops intermittently
Delayed contactor click when charging starts
Code reappears after clearing

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.