P0B9F covers an open or high-resistance sense U lead, channel twenty-one. From U onward the 2012 two-mode trucks drop out, as their pack has only twenty blocks, so this code is a lithium-ion matter at GM. In the eAssist mild hybrid the test is the familiar one, lines N and N-1 both under 1.4 V with a change above 0.5 V within 200 ms in 7 of 10 samples, Type B, but it is now blocked by P1B38 instead of P1B37. The 16OBDG02 programme measures the sense line resistance and sets above 30.00 in 7 of 9 samples, Type A. The 2016 Volt and ELR decide in 0.6 s, the 2019 controller in 0.8 s of 1.6 s, both on adjacent-cell differences of 1.3 V and splice checks.
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 and hybrid or EV system warning
- No start or ready mode on some vehicles
- Charging not possible
Most likely causes
- Sense lead U interrupted or detached from its cell
- Corroded terminal raising the resistance of lead U
- Fault in the balancing circuit used for the channel U test
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 P0B9F means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- B: Subsystem depends on the code range
- 9F: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0B9F?
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 P0B9F?
The most common causes are: sense lead U interrupted or detached from its cell; corroded terminal raising the resistance of lead U; fault in the balancing circuit used for the channel U test.
Related codes
- P0BA0Hybrid/EV Battery Voltage Sense U Circuit Range/Performance
- P0BA1Hybrid/EV Battery Voltage Sense U Circuit Low
- P0BA2Hybrid/EV Battery Voltage Sense U Circuit High
- P0BA3Hybrid/EV Battery Voltage Sense U Circuit Intermittent/Erratic
- P0B9AHybrid/EV Battery Voltage Sense T Circuit
- P0BA4Hybrid/EV Battery Voltage Sense V Circuit
Sources
- gsi.ext.gm.com: 13OBDG05C Hybrid Diagnostics
- gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
- gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
- gsi.ext.gm.com: 19OBDG01 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.