AutoCodes – Chevrolet – P0C78 Chevrolet

P0C78 Chevrolet Code - Hybrid/EV Battery System Precharge Time Too Long

Quick Answer

The hybrid battery system voltage is controlled by two high voltage contactors. Common causes include Faulty Hybrid/EV Battery Pre-Charge Resistor, Faulty Starter/Generator Control Module, Starter/Generator Control Module harness is open or shorted. 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 Chevrolet indicates Hybrid/EV Battery System Precharge Time Too Long.
Common causes: Common causes include Faulty Hybrid/EV Battery Pre-Charge Resistor, Faulty Starter/Generator Control Module, Starter/Generator Control Module harness is open or shorted.
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 2,331

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 Nov 21, 2019

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

The hybrid battery system voltage is controlled by two high voltage contactors. The high voltage contactors allow the high voltage DC batteries to be connected to the vehicle or safely contain the high voltage DC within the Hybrid/EV Battery Pack assembly. Of the two contactors, one is a pre-charge contactor and the other is the primary contactor. The two contactors are closed in a specific sequence by the Starter/Generator Control Module. The pre-charge contactor is closed first. This causes high voltage to flow through the pre-charge resistor, allowing system voltage to build slowly. Once the system voltage has raised and stabilized, the primary contactor is closed. Both contactors are controlled by the Starter/Generator Control Module. The Starter/Generator Control Module supplies B+ to each contactor at all times. When the contactors are to be closed, the Starter/Generator Control Module will provide a ground to the contactor through a low side driver.

OBDII Code P0C78 Chevrolet - Hybrid/EV Battery System Precharge Time Too Long - AutoCodes.com — P0C78 Chevrolet Code - Hybrid/EV Battery System Precharge Time Too Long

What does this mean?

What are the Possible Causes of the DTC P0C78 Chevrolet?

Faulty Hybrid/EV Battery Pre-Charge Resistor
Faulty Starter/Generator Control Module
Starter/Generator Control Module harness is open or shorted
Starter/Generator Control Module circuit poor electrical connection

How to Fix the DTC P0C78 Chevrolet?

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 Chevrolet 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.

Frequently Asked Questions about P0C78 Chevrolet Code

1. What are the common symptoms of OBDII code P0C78 in a Chevrolet hybrid/EV vehicle?

- Common symptoms include a "Service High Voltage Charging System" warning message, reduced hybrid system performance, and potentially a no-start condition.

2. What can cause the OBDII code P0C78 to trigger in a Chevrolet hybrid/EV vehicle?

- The code may be triggered by a malfunction in the hybrid/EV battery system precharge circuit, such as a faulty precharge relay or a high resistance issue.

3. How can I diagnose the cause of OBDII code P0C78 in my Chevrolet hybrid/EV vehicle?

- Diagnosing the code typically involves using a scan tool to check for specific battery system codes, testing the precharge circuit components for proper operation, and inspecting for any loose or damaged connections.

4. Can I still drive my Chevrolet hybrid/EV vehicle with the OBDII code P0C78 present?

- It is not recommended to continue driving the vehicle with this code present, as it may lead to further damage to the hybrid/EV battery system and potentially result in a complete system failure.

5. What are some repair tips for addressing the OBDII code P0C78 in a Chevrolet hybrid/EV vehicle?

- Repair tips may include checking and replacing the precharge relay, inspecting and repairing any damaged wiring or connectors, and ensuring proper communication between the battery management system and other vehicle modules.

6. Is it safe to attempt repairs on the hybrid/EV battery system related to code P0C78 myself?

- Due to the high voltage nature of the hybrid/EV battery system, it is recommended to seek assistance from a qualified technician or dealership for repairs related to this code to ensure safety and proper diagnosis.

7. How much does it typically cost to repair OBDII code P0C78 in a Chevrolet hybrid/EV vehicle?

- The cost of repair can vary depending on the specific cause of the code, but it may involve replacing components like the precharge relay, addressing wiring issues, and potentially recalibrating the battery management system.

8. Can resetting the OBDII code P0C78 in a Chevrolet hybrid/EV vehicle make it go away permanently?

- Resetting the code without addressing the underlying issue will likely result in the code reappearing once the system detects the fault again. It is crucial to diagnose and repair the root cause of the code for a permanent solution.

9. How long does it typically take to repair OBDII code P0C78 in a Chevrolet hybrid/EV vehicle?

- The repair time can vary based on the complexity of the issue, availability of parts, and technician expertise. In some cases, repairs for this code can be completed within a few hours to a day.

10. Are there any preventative maintenance steps I can take to avoid OBDII code P0C78 in my Chevrolet hybrid/EV vehicle?

- Regularly inspecting and maintaining the hybrid/EV battery system, including checking for loose connections, monitoring system performance, and addressing any warning lights promptly, can help prevent issues that may trigger this code.