What Does P0B4C Mean?
DTC P0B4C indicates the hybrid battery voltage sense "D" circuit is reading below the expected voltage at the individual module level. The BMS has detected that the "D" battery module reports abnormally low voltage, suggesting deeply discharged or degraded cells, a wiring fault pulling the sense line low, or a failed cell monitoring circuit. Module-level undervoltage requires prompt attention to prevent permanent cell damage.
Safety Warning
A deeply discharged module can experience cell reversal, leading to internal short circuits and potential thermal runaway. The weakest module limits overall pack performance and can cause cascading degradation of other modules.
Common Causes
30%
Weak or failing cells within the "D" battery module
25%
Corroded or damaged sense wiring causing low voltage reading
20%
Short to ground in the "D" module voltage sense circuit
15%
Faulty cell monitoring IC reading low for the "D" channel
10%
Poor internal cell tab or busbar connection within the module
Diagnostic Steps
1
Retrieve freeze frame data noting SOC, temperature, and load conditions when the fault was set.
2
Compare the "D" module voltage to all other modules via scan tool to quantify the deviation.
3
Measure actual cell voltage at the "D" module terminals and compare to the BMS reading to determine if cells are truly low.
4
Inspect the "D" module sense wiring for shorts to ground, corrosion, or physical damage.
5
If confirmed low cell voltage, perform individual cell testing within the module to identify the weakest cell(s).
6
Check module internal connections for high-resistance joints that could cause abnormal voltage drop under load.
Estimated Repair Cost
$300 - $4,000
Parts + labor, varies by vehicle and location
DTC P0B4C indicates the hybrid battery voltage sense "D" circuit is reading below the expected voltage at the individual module level. The BMS has detected that the "D" battery module reports abnormally low voltage, suggesting deeply discharged or degraded cells, a wiring fault pulling the sense lin...
The most common cause of P0B4C (Hybrid Battery Voltage Sense "D" Circuit Low) is: Weak or failing cells within the "D" battery module
Typical repair costs for P0B4C range from $300 to $4,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A deeply discharged module can experience cell reversal, leading to internal short circuits and potential thermal runaway. The weakest module limits overall pack performance and can cause cascading degradation of other modules.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0B4C to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid/EV Battery System
Difficulty
Type
Generic (SAE)
Recommended Tools
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