AutoCodes – GMC – P1B91 GMC

P1B91 GMC Code - Hybrid/Electric Vehicle Battery 58 Circuit Low Voltage

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: P1B91 GMC indicates Hybrid/Electric Vehicle Battery 58 Circuit Low Voltage.
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 852

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 12, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1B91 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 P1B91 GMC - Hybrid/Electric Vehicle Battery 58 Circuit Low Voltage - AutoCodes.com — P1B91 GMC Code - Hybrid/Electric Vehicle Battery 58 Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P1B91 GMC?

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

How to Fix the DTC P1B91 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 P1B91 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 P1B91 GMC Code

1. What does the OBDII code P1B91 mean on a GMC vehicle?

P1B91 indicates a low voltage issue in the "Hybrid/Electric Vehicle Battery 58 Circuit," which is part of the hybrid or EV battery monitoring system.

2. What are common symptoms of the P1B91 code in a GMC vehicle?

Symptoms may include an illuminated Check Engine or Service Hybrid System light, reduced fuel efficiency, limited hybrid or EV functionality, and potential loss of power.

3. What causes the P1B91 code in GMC vehicles?

Common causes include a faulty battery sensor, damaged or corroded wiring or connectors in the circuit, a failing hybrid/EV battery module, or issues with the battery control module.

4. Can I continue driving with the P1B91 code active?

It's not recommended to drive for extended periods, as this code can indicate issues affecting the hybrid/EV system's performance and reliability. Seek professional diagnosis and repair promptly.

5. How is the P1B91 code diagnosed?

A technician will use a scan tool to verify the code, inspect the battery circuit wiring and connections, test the battery sensor, and check for voltage irregularities in the hybrid/EV battery system.

6. Can a dead or weak 12-volt battery trigger the P1B91 code?

While the 12-volt battery typically doesn't cause this code, itâ€™s good to ensure the auxiliary battery is functioning properly, as it powers essential vehicle systems.

7. How do you fix the P1B91 code on a GMC hybrid or electric vehicle?

Repairs may involve replacing damaged wiring or connectors, repairing the battery control module, or addressing issues with the battery sensor or hybrid/EV battery module.

8. What tools are needed to troubleshoot the P1B91 code?

Required tools may include an OBDII scan tool, a multimeter for voltage testing, and possibly specialized equipment for accessing hybrid or EV battery systems.

9. How much does it cost to repair a P1B91 code on a GMC vehicle?

Costs vary depending on the root cause. Minor repairs like wiring fixes may cost a few hundred dollars, while battery module or control module replacements can be significantly more expensive.

10. Can the P1B91 code clear on its own?

The code is unlikely to clear without addressing the underlying issue. After repairs, the code may need to be manually cleared with an OBDII scan tool.