What Does P0B73 Mean?
DTC P0B73 indicates that the hybrid battery voltage sense circuit for cell group "L" is reporting values outside the expected operating range or is not performing to specification. The BMS receives readings that are within the valid electrical range but deviate from expected values given the current state of charge, temperature, and load conditions. This typically signals gradual cell degradation or a developing connection problem.
Common Causes
30%
Cell imbalance within group L causing voltage deviation from expected values
25%
High-resistance connection at the voltage sense connector or tap point
20%
Battery cells in group L with diminished capacity and altered voltage curve
15%
BMS calibration error or drift in the L channel voltage reference
10%
Temperature sensor fault causing incorrect expected voltage calculation
Diagnostic Steps
1
Review freeze frame data and compare cell group L voltage readings against adjacent groups under the same operating conditions.
2
Perform a manufacturer battery balance/health test to quantify cell group L deviation from the pack average.
3
Clean and inspect the cell group L voltage sense connector, measuring contact resistance to identify high-resistance joints.
4
Measure individual cell voltages within group L using a precision DVOM during rest and under load conditions.
5
Verify the cell temperature sensor for group L is reading accurately, as temperature errors affect expected voltage ranges.
6
If cells are healthy and connections are good, perform a BMS recalibration or software update per manufacturer TSBs.
Estimated Repair Cost
$150 - $3,000
Parts + labor, varies by vehicle and location
DTC P0B73 indicates that the hybrid battery voltage sense circuit for cell group "L" is reporting values outside the expected operating range or is not performing to specification. The BMS receives readings that are within the valid electrical range but deviate from expected values given the current...
The most common cause of P0B73 (Hybrid Battery Voltage Sense "L" Circuit Range/Performance) is: Cell imbalance within group L causing voltage deviation from expected values
Typical repair costs for P0B73 range from $150 to $3,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Range/performance deviations indicate the BMS cannot accurately track cell group L state of charge. This compromises battery longevity through improper balancing and may cause gradual capacity loss. The vehicle may reduce hybrid assist power as a precaution.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0B73 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid/EV Battery System
Difficulty
Type
Generic (SAE)
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