Powertrain, generic · Hybrid propulsion

P0C77 Hybrid/EV Battery System Precharge Time Too Short

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P0C77 is stored when the inverter side reaches battery voltage too quickly during precharge. Before the main contactor closes, the controller charges the inverter capacitor through a precharge resistor and watches the ratio of bus to battery voltage. GM's 2011 Volt sets the code if that ratio passes 95 % within 50 ms of precharge start, Type A; the 2013 eAssist uses 75 ms, Type B, and both require the bus to be below 40 V beforehand. A rise that fast suggests a bypassed or shorted resistor, a main contactor that is welded or closes early, or far less capacitance on the bus than expected. Chrysler lists P0C77 for the 2017 Pacifica Hybrid together with a high-voltage cable that had worked loose on the inverter terminal (08-107-17). Propulsion may be unavailable.

Likely causes

Main contactor welded or closing before precharge ends
Precharge resistor bypassed or shorted
Loose high-voltage cable leaving the inverter capacitor partly disconnected
Faulty bus or battery voltage measurement

Symptoms

  • Malfunction indicator or hybrid warning lamp
  • Vehicle does not become ready or loses 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

P0C78P0C75P0C76P0AE2P0D25

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