P0C78Hybrid/EV Battery System Precharge Time Too Long
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Vehicle does not become ready to drive
- Malfunction indicator lamp and drive system message
- Loss of propulsion
- Likely causes
- LikelyPrecharge resistor, precharge contactor or high-voltage fuse open
- PossibleFaulty high-voltage consumer such as a coolant heater loading the bus
- PossibleBattery module software, fixed by an update
- RareLoose high-voltage cable or bus bar
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.