Powertrain, generic · Hybrid propulsion

P0C78 Hybrid/EV Battery System Precharge Time Too Long

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P0C78 means precharge took too long: the inverter side did not come up to battery voltage within the allowed time. GM's 2011 Volt allows 700 ms to reach 95 % (Type A), the 2013 eAssist 1,000 ms or more than 5 A for over 100 ms (Type B), and the 2019 tables demand 95-105 % at 0.700 s, Type A. The 2018 Outlander PHEV flags a gap of 12 V or more between battery and inverter after 1 s. Typical causes are an open precharge resistor or fuse, a high-voltage load pulling the bus down, and software. Bulletins cover a blown fuse in the service disconnect (Bolt EV, 18-NA-225), a failed coolant heater (Spark EV, 16-NA-072) and battery-module software at Chrysler and Volvo. The vehicle then normally will not become ready.

Likely causes

Precharge resistor, precharge contactor or high-voltage fuse open
Faulty high-voltage consumer such as a coolant heater loading the bus
Battery module software, fixed by an update
Loose high-voltage cable or bus bar

Symptoms

  • Vehicle does not become ready to drive
  • Malfunction indicator lamp and drive system message
  • Loss of propulsion

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,500
Time0.5–5 h

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

Parts involved

hv battery systemprecharge resistormain contactors

Related codes

P0C77P0C76P0C75P0AE3P0D26

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