P0B66 code meaning
Hybrid/EV Battery Voltage Sense I Circuit High
Powertrain system Generic code P0Bxx codes Check engine light
What P0B66 means
When channel I claims a voltage above what its cell or block can physically reach, the controller stores P0B66. The thresholds GM publishes depend on chemistry and architecture: lithium-ion packs with a battery energy control module set it at 4.8 V or more for 1.4 s in a 2 s window, Type A, one trip; the BAS Plus mild hybrid at above 4.65 V in 7 of 10 samples, Type B; the 2012 two-mode trucks, which measure nickel-metal hydride block 9 rather than single cells, above 23 V in 15 of 20 samples, Type B. Every limit sits clearly above normal full charge, so a real overcharged cell is unlikely. Look first for a sense lead touching the next tap up or for a measuring input that has lost its reference.
P0B66 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 8 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0B66
- Charging stops or is refused
- MIL and reduced power
Common causes of P0B66
- Most likelyChannel I lead touching a higher-potential tap
- PossibleOpen reference or ground of the measuring chip
- Less likelyGenuinely overcharged cell after a charging control fault
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv battery voltage sense iWiring harnessBms
What each part of P0B66 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B | Area: hybrid propulsion. |
| 66 | The exact fault in that area. |
What to do next
- Note P0B66 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0B66
What does P0B66 mean?
P0B66 means "Hybrid/EV Battery Voltage Sense I Circuit High". When channel I claims a voltage above what its cell or block can physically reach, the controller stores P0B66. It is a generic code, so it means the same on every make.
Is it safe to drive with P0B66?
Drive gently and only to a workshop. With P0B66 the car can go into limp mode (reduced power) to protect itself.
Will P0B66 fail an emissions test?
Yes, it can. P0B66 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0B66 to fix?
Difficulty: workshop only. A typical repair takes 1 to 8 hours of work. This is a job for a workshop.
Will P0B66 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.