P0B81 code meaning
Hybrid/EV Battery Voltage Sense O Circuit
Powertrain system Generic code P0Bxx codes Check engine light
What P0B81 means
P0B81 stands for an open sense lead on channel O, the fifteenth cell tap. GM has used it from the start: the 2011 Volt battery tables already list P0B81 among the open sense line codes and detect, among other cases, a busbar connection voltage above 0.7 V. In the 2019 battery energy control module the test needs 0.8 s within a 1.6 s window, with adjacent cells 1.3 V or more apart or a balancing gate below 36 mV, Type A. The BAS Plus mild hybrid compares lines N and N-1, both under 1.4 V with a change above 0.5 V in 200 ms, 7 of 10 samples, Type B. Unlike channels M and N, P0B81 does not appear in Ford's Fusion plug-in bulletin. With the lead open, the controller loses sight of that cell and limits operation.
P0B81 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 10 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0B81
- MIL and propulsion system warning
- Reduced power or no electric drive
Common causes of P0B81
- Most likelyLoose or high-resistance busbar joint at the O tap
- PossibleBroken sense wire O in the battery harness
- Less likelyFaulty cell sense module
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 oWiring harnessBms
What each part of P0B81 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. |
| 81 | The exact fault in that area. |
What to do next
- Note P0B81 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 P0B81
What does P0B81 mean?
P0B81 means "Hybrid/EV Battery Voltage Sense O Circuit". P0B81 stands for an open sense lead on channel O, the fifteenth cell tap. It is a generic code, so it means the same on every make.
Is it safe to drive with P0B81?
Drive gently and only to a workshop. With P0B81 the car can go into limp mode (reduced power) to protect itself.
Will P0B81 fail an emissions test?
Yes, it can. P0B81 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 P0B81 to fix?
Difficulty: workshop only. A typical repair takes 1 to 10 hours of work. This is a job for a workshop.
Will P0B81 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.