P0B29: Hybrid/EV Battery B Voltage Low
What to do
As P0B25 — ask what the voltage does after a full charge.
What this code means
Battery B's voltage is below expectation. The discharged-versus-degraded question, and the single check that separates them, are at P0B25.
Likely causes
Start here
- Hybrid battery pack deterioration · specialist
- Weak or failed cell group in the battery pack · specialist
Less common
- Deeply discharged after long-term parking · moderate
- Corroded or loose connector · easy
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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