P0B26: Hybrid/EV Battery A Voltage High
What to do
Treat this as the urgent one in the family. If the car has limited or refused charging, leave it limited — that is protection. Do not fast-charge a vehicle reporting this code, and if it appeared during or just after charging, mention that: it points at the charging equipment rather than the battery. Any smell, heat or swelling around the pack means stop, park away from buildings, and call for help rather than driving on.
What this code means
Battery A's voltage is above what the module expects.
High is the direction that deserves respect. A battery can be flat with no consequence beyond inconvenience; a battery pushed above its designed voltage is being damaged while it happens, and on lithium chemistry the end of that road is thermal runaway. That is why the car's response is usually to stop charging, refuse fast charging, or open the contactors outright — and why those responses should be read as the system working rather than as further faults.
The likeliest cause is not the battery. Something decides how much voltage the battery receives — the on-board charger, the DC/DC converter, the inverter when it is recovering energy under braking — and a control fault in any of them can overcharge a perfectly good pack. So the question is what was doing the charging when the reading went high, and regenerative braking is worth naming explicitly: a pack that is already full and is then handed a long descent has energy pushed into it with nowhere to go.
The other reading, as always, is that the measurement is wrong rather than the voltage. P0B17 carries that argument.
Likely causes
Start here
- Charging system overvoltage · specialist
Less common
- Faulty DC-DC converter · specialist
- Damaged cell voltage sense harness · specialist
- Faulty battery energy control module · specialist
- Faulty battery pack sensor module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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