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DTC codes / P0Bxx · Hybrid propulsion / P0B26

P0B26Hybrid/EV Battery A Voltage High

P0B26 indicates that the hybrid or electric vehicle battery control module has detected an abnormally high voltage condition on battery pack 'A', which is typically the main high-voltage traction battery. The computer compares the measured pack voltage against the expected range for the current state of charge and flags this code when the reading exceeds the upper threshold.

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 driving range or the engine running more often than usual
  • The vehicle entering a fail-safe mode with limited power output
  • A noticeable drop in fuel economy as the hybrid system relies less on the battery
  • In rare cases, a burning smell or physical swelling of the battery pack
  • Often no symptoms besides the warning light, especially if the overvoltage is intermittent

Common causes, most likely first

  1. A faulty voltage sensing circuit or harness between the battery pack and the control module
  2. Degraded or failing cells within the high-voltage battery pack causing voltage imbalance
  3. A malfunctioning battery control module or hybrid vehicle control ECU
  4. Charging system fault that overcharges the pack, such as a stuck contactor or inverter issue
  5. Corroded or loose high-voltage connections at the battery pack terminals
  6. Software calibration error in the battery management system

How to diagnose and fix it

  1. Retrieve all stored codes and freeze-frame data with a scan tool capable of reading hybrid-specific modules
  2. Inspect the high-voltage battery pack, its connectors, and the sensing harness for corrosion, damage, or loose pins
  3. Measure the actual pack voltage with a high-voltage-rated multimeter and compare it to the scan tool's reported value
  4. Check for any related charging system codes and verify the inverter/converter operation
  5. Perform a battery pack voltage balance test if the scan tool supports it, looking for cell group deviations
  6. Reprogram or update the battery control module software if a known calibration bulletin applies
  7. Replace the battery pack, control module, or affected harness only after confirming the fault through voltage measurements and circuit tests

When high voltage is not the battery's fault

  • A loose or corroded voltage sense wire at the battery pack can report a high voltage that the actual cells never produce, so always verify with a direct measurement before condemning the pack.
  • Intermittent P0B26 codes often appear after a charging session or a long downhill regeneration event, pointing to a calibration issue rather than a failed cell.
  • Some vehicles set this code when the 12-volt auxiliary battery is weak because the hybrid control module misreads reference voltages, so check the low-voltage system first.
  • A stuck closed high-voltage contactor can keep the pack connected to the charger or inverter, causing an overvoltage condition that looks like a battery failure but is actually a relay problem.
  • Clearing the code without repairing the root cause can lead to repeated fail-safe activation and, in rare cases, overcharging that damages the pack further.

Can I keep driving with P0B26?

Do not continue driving if the hybrid warning light is accompanied by reduced power or a burning smell, as an overvoltage condition can damage the battery pack and create a safety risk. If the light is on but the vehicle drives normally, limit driving to a short distance to a qualified repair facility and avoid aggressive acceleration or prolonged regenerative braking.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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

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