P0B91: 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. 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.

Symptoms

• MIL on, vehicle often drives normally
• Less electric assist or regenerative braking

Most likely causes

• Measuring channel R reporting a stuck value
• Outdated battery controller or hybrid processor software
• Block 18 or 19 voltage drifting on two-mode NiMH packs

What to check, in order

Start with the simplest. You can tick off each step.

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. Compare the reading with other engine data while varying the engine speed.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. Leave any high-voltage measurements to a specialized repair shop

Good to know

• It can trigger limp mode.
• It affects emissions.

What each character of P0B91 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• B: Subsystem depends on the code range
• 91: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0B91?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0B91?

The most common causes are: measuring channel R reporting a stuck value; outdated battery controller or hybrid processor software; block 18 or 19 voltage drifting on two-mode NiMH packs.

Related codes

• P0B90Hybrid/EV Battery Voltage Sense R Circuit
• P0B92Hybrid/EV Battery Voltage Sense R Circuit Low
• P0B93Hybrid/EV Battery Voltage Sense R Circuit High
• P0B94Hybrid/EV Battery Voltage Sense R Circuit Intermittent/Erratic
• P0B8CHybrid/EV Battery Voltage Sense Q Circuit Range/Performance
• P0B96Hybrid/EV Battery Voltage Sense S Circuit Range/Performance
• P0ABBHybrid/EV Battery Pack Voltage Sense A Circuit Range/Performance

Sources

• gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics
• gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
• gsi.ext.gm.com: 12OBDG06 Hybrid Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.