AutoCodes – Cadillac – P0C78 Cadillac

P0C78 Cadillac 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 Cadillac 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 989

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

What does this mean?

What are the Possible Causes of the DTC P0C78 Cadillac?

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 Cadillac?

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 Cadillac 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.

Need more information about the P0C78 Cadillac code?

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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 Cadillac Code

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

The common symptoms of OBDII code P0C78 include reduced hybrid system performance, decreased fuel efficiency, and potential illumination of the check engine light.

2. What does the OBDII code P0C78 indicating "Hybrid/EV Battery System Precharge Time Too Long" mean?

The code P0C78 indicates that the precharge time for the hybrid/EV battery system in a Cadillac vehicle is taking longer than the expected parameters.

3. What are the possible causes of OBDII code P0C78 in a Cadillac hybrid vehicle?

Possible causes of code P0C78 include issues with the hybrid battery pack, faulty precharge circuitry, wiring problems, or a malfunctioning hybrid control module.

4. How can I diagnose OBDII code P0C78 in my Cadillac hybrid vehicle?

Diagnosing OBDII code P0C78 typically involves using a professional OBDII scanner to read the code, checking the hybrid battery system components for faults, and performing a thorough inspection of the precharge system.

5. How serious is OBDII code P0C78 in a Cadillac hybrid/EV vehicle?

While the vehicle may still be operable with code P0C78, it is important to address this issue promptly to prevent further damage to the hybrid battery system and to ensure optimal performance of the vehicle.

6. Can I continue driving my Cadillac with OBDII code P0C78?

It is not recommended to continue driving your Cadillac with OBDII code P0C78, as prolonged precharge time can lead to potential issues with the hybrid system and may cause further damage.

7. How can I repair OBDII code P0C78 in my Cadillac hybrid vehicle?

Repairing OBDII code P0C78 may involve replacing faulty components in the precharge system, repairing wiring issues, or reprogramming the hybrid control module to correct the precharge time.

8. Is it possible to reset OBDII code P0C78 in a Cadillac hybrid vehicle?

Resetting the OBDII code P0C78 can be done using a professional OBDII scanner after repairing the underlying issue causing the code to appear.

9. Are there any maintenance tips to prevent OBDII code P0C78 in a Cadillac hybrid vehicle?

Regularly servicing the hybrid battery system, checking the precharge system components for wear, and addressing any warning signs promptly can help prevent OBDII code P0C78 from appearing.

10. How much does it typically cost to repair OBDII code P0C78 in a Cadillac hybrid vehicle?

The cost of repairing OBDII code P0C78 can vary depending on the specific issue causing the code, the labor rates in your area, and whether any components need to be replaced. It is recommended to consult with a professional mechanic for an accurate estimate.