P0B91 code meaning
Hybrid/EV Battery Voltage Sense R Circuit Range/Performance
Powertrain system Generic code P0Bxx codes Check engine light
What P0B91 means
Here the wiring of sense R is intact, but its value does not behave like a real cell. GM's 2019 hybrid powertrain processor demands that cell R moves at least 0.005 V in the same direction whenever the cell average shifts by more than 0.022 V; 35 failures out of 40 samples at 100 ms give a Type A fault. The 2016 Volt allows 7 s of failure in an 8 s window, the ELR 20 of 40 samples at 200 ms. On the 2012 two-mode trucks R is nickel-metal hydride block 18: blocks 18 and 19 are each multiplied by twenty, and if both estimates miss the pack voltage by more than 70 V in 160 of 170 samples, P0B91 is set as Type B. A frozen measuring channel or controller software is the usual suspect.
P0B91 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0B91
- MIL on, vehicle often drives normally
- Less electric assist or regenerative braking
Common causes of P0B91
- Most likelyMeasuring channel R reporting a stuck value
- PossibleOutdated battery controller or hybrid processor software
- Less likelyBlock 18 or 19 voltage drifting on two-mode NiMH packs
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 rWiring harnessBms
What each part of P0B91 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. |
| 91 | The exact fault in that area. |
What to do next
- Note P0B91 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 P0B91
What does P0B91 mean?
P0B91 means "Hybrid/EV Battery Voltage Sense R Circuit Range/Performance". Here the wiring of sense R is intact, but its value does not behave like a real cell. It is a generic code, so it means the same on every make.
Is it safe to drive with P0B91?
Drive gently and only to a workshop. With P0B91 the car can go into limp mode (reduced power) to protect itself.
Will P0B91 fail an emissions test?
Yes, it can. P0B91 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 P0B91 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will P0B91 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.