Faulty or damaged voltage sense wire (open, shorted, or high resistance) on circuit L; Corroded or loose connector pins at the battery pack sense harness or module interface; Failed cell voltage sensor or battery monitoring module internal fault; Poor terminal contact at the battery pack service disconnect or interlock; Battery pack internal wiring damage from vibration, heat, or moisture intrusion; Software or calibration issue in the battery energy control module (rare but possible)

DTC codes / P0Bxx · Hybrid propulsion / P0B73

P0B73Hybrid/EV Battery Voltage Sense L Circuit Range/Performance

Q: What does code P0B73 mean?

Hybrid/EV Battery Voltage Sense L Circuit Range/Performance. P0B73 indicates that the hybrid or electric vehicle battery pack monitoring system has detected an abnormal voltage reading on the voltage sense circuit labeled 'L', which is one of several sense lines used to measure individual cell or module voltages. The computer compares this signal against expected values and flags a range or performance fault when the reading falls outside the allowable window or behaves erratically.

P0B73 indicates that the hybrid or electric vehicle battery pack monitoring system has detected an abnormal voltage reading on the voltage sense circuit labeled 'L', which is one of several sense lines used to measure individual cell or module voltages. The computer compares this signal against expected values and flags a range or performance fault when the reading falls outside the allowable window or behaves erratically.

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
Often no symptoms besides the warning light, especially in early stages
Reduced electric-only range or the vehicle refusing to enter EV mode
Intermittent loss of power or a sudden transition to limp-home mode
Inaccurate state-of-charge display or erratic battery gauge behavior
Possible charging faults or the vehicle failing to start in some cases

Common causes, most likely first

Faulty or damaged voltage sense wire (open, shorted, or high resistance) on circuit L
Corroded or loose connector pins at the battery pack sense harness or module interface
Failed cell voltage sensor or battery monitoring module internal fault
Poor terminal contact at the battery pack service disconnect or interlock
Battery pack internal wiring damage from vibration, heat, or moisture intrusion
Software or calibration issue in the battery energy control module (rare but possible)

How to diagnose and fix it

Retrieve all stored codes and freeze-frame data, then clear codes and test-drive to see if P0B73 returns immediately or intermittently
Inspect the sense circuit L wiring and connectors for chafing, corrosion, or loose pins, especially at the battery pack and module connectors
Measure resistance and voltage drop on the sense line from the module to the battery energy control module (BECM) and compare to specifications
Swap the sense lead with a known-good adjacent circuit (if accessible) to isolate whether the fault follows the wire or stays with the module
Perform a battery pack voltage measurement at the sense terminals and compare with the BECM reported value to identify signal skew
If wiring and connectors are good, test or replace the affected cell voltage sensor or battery monitoring module per manufacturer procedures
After repair, clear codes and perform a battery pack relearn or calibration drive cycle as required

Sense circuit faults often mimic module failure

A loose or corroded connector pin on the sense harness is far more common than a failed battery module, so always perform a wiggle test and pin drag test before condemning expensive components.
The code can set intermittently due to vibration or temperature changes, so a static resistance check may pass while the fault only appears during a road test over rough surfaces.
Some vehicles set P0B73 when the 12-volt auxiliary battery is weak or the charging system is unstable, because the BECM reference voltage becomes unreliable.
Replacing a battery module without first verifying the sense circuit integrity can lead to a repeat failure and unnecessary expense, as the new module will report the same fault if the wiring is still bad.
On some platforms, a software update to the BECM addresses false range/performance faults without any hardware replacement, so check for technical service bulletins before parts swapping.

Can I keep driving with P0B73?

The vehicle may remain driveable with reduced electric performance, but continued driving risks a sudden loss of power or limp mode, so limit use and avoid heavy acceleration or long trips until the fault is diagnosed. If the warning light flashes or the vehicle enters limp mode, stop driving and arrange service.

Tools that help

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