AutoCodes – Toyota – P0C78 Toyota

P0C78 Toyota Code - Hybrid Battery System Precharge Time Too Long

Quick Answer

The inverter contains a three-phase bridge circuit, which consists of six power transistors (IGBTs) each for MG1 and MG2. Common causes include Faulty Inverter with converter assembly, Inverter with converter assembly harness is open or shorted, Inverter with converter assembly circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0C78 Toyota indicates Hybrid Battery System Precharge Time Too Long.
Common causes: Common causes include Faulty Inverter with converter assembly, Inverter with converter assembly harness is open or shorted, Inverter with converter assembly circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 1,656

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Feb 13, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P0C78 Toyota Description

The inverter contains a three-phase bridge circuit, which consists of six power transistors (IGBTs) each for MG1 and MG2. The inverter converts high-voltage direct current from the HV battery into three-phase alternating current for generator (MG1) and motor (MG2); it also converts three-phase alternating current supplied by generator (MG1) and motor (MG2) into direct current for the HV battery. The MG ECU controls the actuation of the power transistors (IGBTs). The inverter transmits information necessary for control, such as amperage and voltage, to the MG ECU.

OBDII Code P0C78 Toyota - Hybrid Battery System Precharge Time Too Long - AutoCodes.com — P0C78 Toyota Code - Hybrid Battery System Precharge Time Too Long

What does this mean?

What are the Possible Causes of the DTC P0C78 Toyota?

Faulty Inverter with converter assembly
Inverter with converter assembly harness is open or shorted
Inverter with converter assembly circuit poor electrical connection
Faulty Power management control ECU

How to Fix the DTC P0C78 Toyota?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0C78 Toyota code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.