P0B56Hybrid/EV Battery Voltage Sense F Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- The GM two-mode hybrids of 2012, Tahoe, Yukon, Escalade, Silverado and Sierra, show a detail of P0B56 that lithium-ion packs lack. Their nickel-metal hydride pack is read in blocks, channel F being block 6, and the battery pack control module sets the code only when block 6 and block 7 both read under 2 V in 15 of 20 samples at 100 ms, Type B, two trips; a shared sense wire between the blocks is the obvious suspect then. In GM's lithium-ion systems the battery energy control module uses 0.2 V or less on cell voltage F for 1.4 s within 2 s, Type A. In both cases the controller assumes a failed measurement and reduces battery use until repair.
- What you may notice
- Hybrid system warning, MIL after the second drive (two-mode)
- Engine runs continuously, no electric launch
- Lower fuel economy
- Likely causes
- LikelyFault in the sense wire shared by blocks 6 and 7 (GM two-mode)
- PossibleChannel F sense line shorted to a neighbouring line
- PossibleFailed input on the cell monitoring electronics
- 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: €50 – €5,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.