P0B51Hybrid/EV Battery Voltage Sense E 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
- P0B51 tells that cell sense channel E reads near zero. GM's battery energy control module only runs this check under clear conditions: the module is in run, crank or accessory mode, the second protection self-test is not running, and no slave communication, open sense line, balancing or internal performance fault is active. Then a reading of 0.2 V or less for 1.4 s in a 2 s window sets the code, Type A, one trip. The order matters for diagnosis: an open sense line or a lost slave board would be reported first by their own codes. On the 2012 two-mode hybrids channel E is block 5, set when blocks 5 and 6 both drop below 2 V, Type B. Electric operation is then restricted.
- What you may notice
- MIL and hybrid system warning
- Electric-only driving unavailable
- Likely causes
- LikelyChannel E sense line shorted to its neighbour
- PossibleFaulty input on the cell monitoring slave board
- RarePin backed out of the monitoring harness connector
- 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.