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DTC codes / P0Bxx · Hybrid propulsion / P0B72

P0B72Hybrid/EV Battery Voltage Sense L Circuit

P0B72 indicates that the hybrid or electric vehicle battery control module has detected an abnormal voltage reading on the voltage sense circuit for battery module or cell group 'L'. The computer compares this sensed voltage against expected values and flags the circuit as faulty when the signal is out of range, erratic, or missing.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the hybrid system warning light or service vehicle soon message
  • Reduced electric-only driving range or the vehicle refusing to enter EV mode
  • Inconsistent state-of-charge readings or sudden drops in indicated battery level
  • Powertrain derangement with limited power output or forced engine-only operation
  • Often no symptoms besides the warning light, especially in early stages

Common causes, most likely first

  1. Damaged or chafed wiring in the voltage sense harness between the battery module and the control unit
  2. Corroded or loose connector terminals at the battery module sense connector
  3. Faulty voltage sense circuit within the battery pack, such as a failed sense wire or internal module connection
  4. Failed hybrid battery control module or battery energy control module
  5. High-voltage battery module degradation causing out-of-range cell voltages
  6. Water intrusion or contamination in the battery pack connector area

How to diagnose and fix it

  1. Retrieve all stored codes and freeze-frame data with a scan tool capable of hybrid battery diagnostics
  2. Inspect the voltage sense harness and connectors at the affected battery module for damage, corrosion, or loose pins
  3. Measure resistance and continuity of the sense circuit from the module connector to the control unit
  4. Compare live voltage readings for module 'L' against adjacent modules to identify a single-cell or wiring discrepancy
  5. Perform a battery pack voltage measurement at the module terminals to verify the sensed value
  6. If wiring and connectors are good, test or substitute the battery control module per manufacturer procedures
  7. Clear codes and perform a hybrid battery relearn or adaptation drive cycle to confirm the repair

Voltage sense faults that mimic module failure

  • A single chafed sense wire can set P0B72 while the battery module itself is perfectly healthy, so always verify circuit integrity before condemning the pack.
  • Technicians often overlook corrosion inside the battery pack connector housing, which can introduce resistance that skews the voltage reading without any visible external damage.
  • This code can be set by a weak 12-volt auxiliary battery causing low reference voltage to the hybrid control module, so check system voltage first.
  • After replacing a sense harness or module, some vehicles require a battery pack capacity relearn or the code will reset immediately on the next key cycle.
  • P0B72 is sometimes stored alongside multiple other voltage sense codes when the root cause is a shared ground or reference circuit rather than the 'L' circuit alone.

Can I keep driving with P0B72?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration, prolonged EV-only operation, and any attempt to charge the high-voltage battery until the fault is diagnosed. Continued driving with a voltage sense fault may cause the hybrid system to disable and leave you stranded.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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