Powertrain, generic · Hybrid propulsion

P0C76 Hybrid/EV Battery System Discharge Time Too Long

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P0C76 means the high-voltage bus is still too high a set time after the contactors opened, so the inverter capacitor was not drained as intended. GM publishes thresholds: the 2011 Volt flags more than 200 V after 3.5 s (Special Type C, no MIL), the 2013 eAssist cars more than 65 V after 6.5 s and the 2019 tables more than 200 V after 3.5 s, both Type A after two failed runs. Bulletins name welded contactors on the 2019 Volt (software update, N192226060), a high-voltage cable that had worked loose on the inverter terminal of the 2017 Pacifica Hybrid (08-107-17) and, on GM two-mode trucks, jump-starting with the key on (PIT4585E). A failed discharge circuit is the classic part fault. Treat the bus as live until measured.

Likely causes

Active discharge circuit or discharge resistor in the inverter failed
Main contactor welded closed so the battery keeps feeding the bus
Loose high-voltage cable or terminal at the inverter
Low 12 V supply during shutdown or module software

Symptoms

  • Hybrid warning lamp or service high voltage message
  • Vehicle may not start or become ready
  • Loss of propulsion

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–3,000
Time0.5–6 h

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

Parts involved

hv battery systemdischarge resistormain contactors

Related codes

P0C75P0C77P0C78P0AA1P0AA4

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.