P0B9A is the open-circuit code for sense T, the twentieth cell channel. GM uses it only on lithium-ion packs. The 2011 Volt compares adjacent cells for a difference above 1 V and checks the busbar cap voltage against 0.7 V; the 2016 Volt and ELR raise the adjacent-cell limit to 1.3 V, add a balancing-gate test below 36 mV and decide within 0.6 s, and the 2019 controller keeps those values but stretches the window to 0.8 s of 1.6 s, Type A in both cases. The 2012 two-mode trucks also have a channel T, their last nickel-metal hydride block 20, yet their tables carry range, low and high codes for it and no circuit code. A genuinely open lead usually means opening the high-voltage pack.
High severity. Can I keep driving?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.
Symptoms
- MIL, hybrid or EV system warning
- Ready mode or charging blocked
Most likely causes
- Open sense lead T at the cell tab or connector
- Poor busbar or splice joint in the channel T path
- Monitoring board input for channel T failed
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- It can trigger limp mode.
- It affects emissions.
What each character of P0B9A means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- B: Subsystem depends on the code range
- 9A: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0B9A?
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 P0B9A?
The most common causes are: open sense lead T at the cell tab or connector; poor busbar or splice joint in the channel T path; monitoring board input for channel T failed.
Related codes
- P0B9BHybrid/EV Battery Voltage Sense T Circuit Range/Performance
- P0B9CHybrid/EV Battery Voltage Sense T Circuit Low
- P0B9DHybrid/EV Battery Voltage Sense T Circuit High
- P0B9EHybrid/EV Battery Voltage Sense T Circuit Intermittent/Erratic
- P0B95Hybrid/EV Battery Voltage Sense S Circuit
- P0B9FHybrid/EV Battery Voltage Sense U Circuit
Sources
- gsi.ext.gm.com: 11OBDG01 HYBRID Diagnostics
- gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
- gsi.ext.gm.com: 19OBDG01 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.