P0C78 code meaning
Hybrid/EV Battery System Precharge Time Too Long
Powertrain system Generic code P0Cxx codes Check engine light
What P0C78 means
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.
P0C78 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0C78
- Vehicle does not become ready to drive
- Malfunction indicator lamp and drive system message
- Loss of propulsion
Common causes of P0C78
- Most 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
- Less likelyLoose high-voltage cable or bus bar
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv battery systemPrecharge resistorMain contactors
What each part of P0C78 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| C | Area: hybrid propulsion. |
| 78 | The exact fault in that area. |
What to do next
- Note P0C78 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0C78
What does P0C78 mean?
P0C78 means "Hybrid/EV Battery System Precharge Time Too Long". P0C78 means precharge took too long: the inverter side did not come up to battery voltage within the allowed time. It is a generic code, so it means the same on every make.
Is it safe to drive with P0C78?
Drive gently and only to a workshop. With P0C78 the car can go into limp mode (reduced power) to protect itself.
Will P0C78 fail an emissions test?
Yes, it can. P0C78 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0C78 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 5 hours of work. This is a job for a workshop.
Will P0C78 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.