AutoCodes – Cadillac – P1B21 Cadillac

P1B21 Cadillac Code - Hybrid/Electric Vehicle Battery 30 Circuit High 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: P1B21 Cadillac indicates Hybrid/Electric Vehicle Battery 30 Circuit High 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 837

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 08, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1B21 Cadillac 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 P1B21 Cadillac - Hybrid/Electric Vehicle Battery 30 Circuit High Voltage - AutoCodes.com — P1B21 Cadillac Code - Hybrid/Electric Vehicle Battery 30 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P1B21 Cadillac?

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

How to Fix the DTC P1B21 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 P1B21 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.

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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 P1B21 Cadillac Code

1. What does the OBDII code P1B21 mean on a Cadillac?

P1B21 indicates an issue with the Hybrid/Electric Vehicle Battery 30 circuit, specifically detecting high voltage beyond the normal operating range.

2. What are the common symptoms of code P1B21 on a Cadillac?

Symptoms may include an illuminated check engine light, reduced hybrid or EV system performance, limited driving range, or the vehicle entering limp mode.

3. What causes the P1B21 code to appear on a Cadillac?

Common causes include a faulty battery module, damaged wiring or connectors in the battery circuit, or a malfunctioning battery energy control module.

4. Can a loose connection cause the P1B21 code on my Cadillac?

Yes, loose or corroded connections in the battery circuit can disrupt voltage levels and trigger the P1B21 code.

5. How is code P1B21 diagnosed on a Cadillac?

A technician will use a scan tool to confirm the code, inspect the battery circuit wiring and connectors, and test the voltage levels at the battery module and control module.

6. Is it safe to drive with the P1B21 code on a Cadillac?

Driving with this code is not recommended, as it can lead to further damage to the hybrid or electric system and may reduce vehicle performance or reliability.

7. How do you fix the P1B21 code on a Cadillac?

Repairs may include replacing a faulty battery module, repairing damaged wiring, cleaning or securing loose connections, or reprogramming the battery control module.

8. Can the P1B21 code clear itself on a Cadillac?

The code may clear temporarily if the issue is intermittent, but it will likely return until the underlying problem is resolved.

9. What tools are needed to troubleshoot the P1B21 code on a Cadillac?

A scan tool capable of reading hybrid system codes, a multimeter for voltage testing, and access to the vehicleâ€™s wiring diagrams are essential for diagnosing this code.

10. Does the P1B21 code indicate a need for a new hybrid battery on a Cadillac?

Not necessarily. While the hybrid battery could be at fault, the issue might also stem from wiring, connections, or the battery control module. Proper diagnosis is required.