System: Powertrain (P-Code)
SAE Standard (Generic)
Family: HV Battery Precharge Discharge Timing
Code P0C78: Hybrid/EV Battery System Precharge Time Too Long
Diagnostic & Technical Explanation
Code P0C78 sets when the HV battery main contactor precharge/discharge circuit does not complete its resistor-limited precharge or its controlled discharge within the time window the control module expects before or after main-contactor closure. The most common physical causes are a burned-open precharge resistor, a precharge relay that sticks or fails to energize, and an unexpected downstream short or leakage path loading the bus.
First-listed procedure
Rank #1
Review scan-tool precharge/discharge timing data
Moderate DIY
This is the first procedure in the authored
consideration order, not a measured cause likelihood. Execute it only when its prerequisites
and diagnostic findings support it. Its cost and labor estimates (where known), the step-by-step procedure and the
remaining 2 procedure(s) are in the licensed dataset. Ordering context.
Full family: HV Battery Precharge Discharge Timing
What this page does not show
This page publishes the fault mechanism and the code index. The licensed dataset adds, for
every one of the 15,886 codes, the full authored repair set (56,729 procedures in total)
with the fields deliberately withheld here:
- Procedures 2..n after the first-listed procedure
- Aftermarket parts cost ranges in USD (
est_parts_cost_min/max_usd)
- Professional labor-hour estimates (
est_labor_hours)
- Step-by-step diagnostic and repair instructions
- Replacement-part mappings and catalog lookups
- 6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)