Cause
Weak or failed cell group in the battery pack
One section of the traction battery has lost capacity, developed high internal resistance, or failed outright, while the rest of the pack remains serviceable.
A pack is a long series string, and a series string is only as good as its worst member. Every cell group carries the same current, so the weakest one reaches its lower limit first on discharge and its upper limit first on charge. The module has to protect it, which means the whole pack stops early in both directions — so one bad section out of many presents as a pack that has lost a large part of its usable range. The car is not exaggerating and the other sections are not faulty; the arithmetic of a series string simply works that way.
The characteristic signature is divergence under load rather than a low number at rest. A weak group often looks acceptable sitting still and drops away sharply the moment current is drawn, recovering when the load goes — which is high internal resistance rather than lost capacity, and the two are distinguishable if anyone bothers to look.
Whether this ends in a module or a whole pack depends on the vehicle, and it is the question to ask. Many designs allow a single failed module to be replaced and the pack rebalanced, at a fraction of the cost of a new one; some do not. Before accepting a complete pack quote, ask whether module-level replacement is supported — and confirm the sense wiring has been eliminated first, because a faulty measuring wire produces exactly the same reading.
Typically specialist work. Needs equipment or training most home workshops do not have.
Some of these codes mean you should stop driving
5 of the 227 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (227)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0B25 Hybrid/EV Battery A Voltage Low Likely for this code High
- P0B29 Hybrid/EV Battery B Voltage Low Likely for this code High
- P0B2D Hybrid/EV Battery C Voltage Low Likely for this code High
- P0B31 Hybrid/EV Battery D Voltage Low Likely for this code High
- P0B3C Hybrid/EV Battery Voltage Sense A Circuit Range/Performance Likely for this code High
- P0B41 Hybrid/EV Battery Voltage Sense B Circuit Range/Performance Likely for this code High
- P0B46 Hybrid/EV Battery Voltage Sense C Circuit Range/Performance Likely for this code High
- P0B4B Hybrid/EV Battery Voltage Sense D Circuit Range/Performance Likely for this code High
- P0B50 Hybrid/EV Battery Voltage Sense E Circuit Range/Performance Likely for this code High
- P0B55 Hybrid/EV Battery Voltage Sense F Circuit Range/Performance Likely for this code High
- P0B5A Hybrid/EV Battery Voltage Sense G Circuit Range/Performance Likely for this code High
- P0B5F Hybrid/EV Battery Voltage Sense H Circuit Range/Performance Likely for this code High
- P0B64 Hybrid/EV Battery Voltage Sense I Circuit Range/Performance Likely for this code High
- P0B69 Hybrid/EV Battery Voltage Sense J Circuit Range/Performance Likely for this code High
- P0B6E Hybrid/EV Battery Voltage Sense K Circuit Range/Performance Likely for this code High
- P0B73 Hybrid/EV Battery Voltage Sense L Circuit Range/Performance Likely for this code High
- P0B78 Hybrid/EV Battery Voltage Sense M Circuit Range/Performance Likely for this code High
- P0B7D Hybrid/EV Battery Voltage Sense N Circuit Range/Performance Likely for this code High
- P0B82 Hybrid/EV Battery Voltage Sense O Circuit Range/Performance Likely for this code High
- P0B87 Hybrid/EV Battery Voltage Sense P Circuit Range/Performance Likely for this code High
- P0B8C Hybrid/EV Battery Voltage Sense Q Circuit Range/Performance Likely for this code High
- P0B91 Hybrid/EV Battery Voltage Sense R Circuit Range/Performance Likely for this code High
- P0B96 Hybrid/EV Battery Voltage Sense S Circuit Range/Performance Likely for this code High
- P0B9B Hybrid/EV Battery Voltage Sense T Circuit Range/Performance Likely for this code High
- P0BA0 Hybrid/EV Battery Voltage Sense U Circuit Range/Performance Likely for this code High
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.
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- The car — make, model, year and engine. The same fault behaves differently on each.
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