A weak or failing cell or module within the high-voltage battery pack; Poor electrical connection at the battery pack terminals or intermodule bus bars; A faulty battery pack voltage sensor or wiring harness; Degradation of the battery pack due to age, heat, or repeated deep discharges; An issue with the battery energy control module (BECM) or its power supply; Extreme cold temperatures temporarily reducing battery voltage; A parasitic draw that leaves the pack at a low state of charge

DTC codes / P0Bxx · Hybrid propulsion / P0B25

P0B25Hybrid/EV Battery A Voltage Low

Q: What does code P0B25 mean?

Hybrid/EV Battery A Voltage Low. P0B25 indicates that the hybrid or electric vehicle battery control module has detected an abnormally low voltage on battery pack 'A', which is typically the main high-voltage traction battery. The computer compares the measured pack voltage against expected values and sets this code when the reading falls below the calibrated threshold for a specified time.

P0B25 indicates that the hybrid or electric vehicle battery control module has detected an abnormally low voltage on battery pack 'A', which is typically the main high-voltage traction battery. The computer compares the measured pack voltage against expected values and sets this code when the reading falls below the calibrated threshold for a specified time.

SystemPowertrain

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the hybrid system warning light or service vehicle soon message
Reduced electric-only range or the engine running more frequently than usual
A noticeable drop in acceleration or power output, especially under load
The vehicle may enter a fail-safe mode that limits speed or disables hybrid operation
Often no symptoms besides the warning light, particularly if the voltage drop is intermittent
In some cases, the vehicle may refuse to start or shift into gear

Common causes, most likely first

A weak or failing cell or module within the high-voltage battery pack
Poor electrical connection at the battery pack terminals or intermodule bus bars
A faulty battery pack voltage sensor or wiring harness
Degradation of the battery pack due to age, heat, or repeated deep discharges
An issue with the battery energy control module (BECM) or its power supply
Extreme cold temperatures temporarily reducing battery voltage
A parasitic draw that leaves the pack at a low state of charge

How to diagnose and fix it

Use a scan tool to retrieve all stored codes and freeze-frame data, then verify the battery pack voltage with a high-voltage meter if safe and qualified
Inspect the low-voltage battery and charging system, as a weak 12V battery can cause false low-voltage readings
Check the high-voltage battery pack terminals and intermodule connections for corrosion, looseness, or damage
Perform a battery pack state-of-health test using the manufacturer's diagnostic software to identify weak modules
Test the battery pack voltage sensor and its wiring for continuity and correct reference voltage
If a weak module is confirmed, replace the affected module or the entire pack according to manufacturer procedures
Clear the codes and perform a battery pack relearn or calibration drive cycle as required

What a low pack voltage reading really means

A low voltage code often originates from a single weak cell or module rather than the entire pack, so module-level testing is critical before condemning the whole battery.
Corroded or loose intermodule bus bars can create resistance that mimics a failing cell, and tightening or cleaning them may resolve the code without parts replacement.
The battery energy control module may set this code due to a faulty voltage sensor even when the pack is healthy, so always verify actual voltage with a calibrated meter.
Cold weather can temporarily lower pack voltage enough to trigger this code, and the light may clear once the battery warms up, but repeated occurrences indicate a real issue.
A weak 12-volt auxiliary battery can cause erratic behavior in the hybrid control system and set false low-voltage codes, so always load-test the 12V battery first.

Can I keep driving with P0B25?

Do not continue driving with this code if the hybrid system warning is active or the vehicle is in fail-safe mode, as a failing high-voltage battery can leave you stranded or cause further damage. If the light is on but the vehicle drives normally, limit driving to reach a qualified repair facility and avoid heavy acceleration or long trips.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.