AutoCodes – GMC – P1E79 GMC

P1E79 GMC Code - Hybrid/Electric Vehicle Battery 78 Circuit

Quick Answer

The Hybrid/Electric Vehicle battery pack contains 288 cells. Common causes include Faulty Hybrid/Electric Vehicle Battery Pack, Faulty Hybrid/Electric Vehicle Battery Interface Control Module. 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: P1E79 GMC indicates Hybrid/Electric Vehicle Battery 78 Circuit.
Common causes: Common causes include Faulty Hybrid/Electric Vehicle Battery Pack, Faulty Hybrid/Electric Vehicle Battery Interface Control Module.
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 767

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 Mar 14, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1E79 GMC Description

The Hybrid/Electric Vehicle battery pack contains 288 cells. Groups of three cells are welded together in parallel. There are a total of 96 cell groups in the hybrid/EV battery pack assembly. These cell groups are electrically connected in-series. Each individual cell group is rated at 3.7 V, for a nominal system voltage of 355 V direct current. The battery cells are also grouped together into three sections. The first 90 cells/30 cell groups make up battery section one. This section is adjacent to the cowl and contains batteries 67 through to 96. Battery section two is located behind section one. It is made up of 72 cells/24 cell groups and contains batteries 43 through to 66. The transverse battery section is section number three, it is made up of the remaining 126 cells/42 cell groups and contains batteries 1 through to 42. The three battery sections are individually serviceable components.
The battery energy control module monitors the voltage of the 96 battery cell groups through the four hybrid/EV battery interface control modules. Voltage sense circuits are attached to each individual cell group, and these sense circuits terminate at a connector located on the top surface of the battery section. A serviceable auxiliary battery wiring harness joins this connector to a hybrid/EV battery interface control module, also located on the top surface of the battery section. The hybrid/EV battery interface control module encodes the voltage reading and transmits it to the battery energy control module through the battery control harness. There is one hybrid/EV battery interface control module located on battery sections one and two, and two hybrid/EV battery interface control modules associated with battery section three. The hybrid/EV battery interface control module, battery energy control module wiring harness, auxiliary battery wiring harness, and battery energy control module are all considered serviceable components.
The battery energy control module will determine when a fault condition is present. Diagnostics and system status are communicated from the battery energy control module to hybrid/EV powertrain control module 2 through serial data. The hybrid/EV powertrain control module 2 is the host controller for diagnostic trouble code information.

OBDII Code P1E79 GMC - Hybrid/Electric Vehicle Battery 78 Circuit - AutoCodes.com — P1E79 GMC Code - Hybrid/Electric Vehicle Battery 78 Circuit

What does this mean?

What are the Possible Causes of the DTC P1E79 GMC?

Faulty Hybrid/Electric Vehicle Battery Pack
Faulty Hybrid/Electric Vehicle Battery Interface Control Module

How to Fix the DTC P1E79 GMC?

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 P1E79 GMC 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 P1E79 GMC Code

1. What does the OBDII code P1E79 mean on a GMC vehicle?

P1E79 indicates an issue with the Hybrid/Electric Vehicle Battery 78 Circuit, which typically relates to a malfunction in the high-voltage battery system.

2. What are the common symptoms of the P1E79 code?

Symptoms may include a "Check Engine" light, reduced hybrid or electric performance, decreased fuel efficiency, or the inability to use electric-only mode.

3. What causes the P1E79 code to appear?

The code is usually triggered by issues like faulty battery cells, damaged wiring or connectors in the battery circuit, or a malfunctioning battery management system.

4. Can I drive my GMC with a P1E79 code?

Driving with this code is not recommended as it may lead to reduced performance, potential damage to the hybrid/electric system, or even safety risks.

5. How is the P1E79 code diagnosed?

A technician will use a scan tool to check for the code, inspect the battery wiring and connectors, and evaluate the condition of the high-voltage battery and related components.

6. What repairs are needed to fix the P1E79 code?

Repairs may include replacing damaged wiring, repairing or replacing the high-voltage battery, or updating/reprogramming the battery management system.

7. How much does it cost to repair a P1E79 code on a GMC?

Repair costs vary widely depending on the root cause. Minor issues like wiring repairs may cost a few hundred dollars, while high-voltage battery replacement can cost several thousand dollars.

8. Can a low 12-volt battery cause the P1E79 code?

While unlikely, a weak 12-volt battery can sometimes affect the hybrid systemâ€™s operation and should be checked as part of the diagnostic process.

9. Will clearing the P1E79 code fix the problem?

Clearing the code will reset the warning light, but the underlying issue must be repaired to prevent the code from returning.

10. Is the P1E79 code covered under warranty?

Depending on your vehicleâ€™s hybrid system warranty, repairs related to the high-voltage battery may be covered. Check with your dealer for specific warranty details.