P0B9AHybrid/EV Battery Voltage Sense T Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- MIL, hybrid or EV system warning
- Ready mode or charging blocked
- Likely causes
- LikelyOpen sense lead T at the cell tab or connector
- PossiblePoor busbar or splice joint in the channel T path
- RareMonitoring board input for channel T failed
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €150 – €7,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.