What Does P0B29 Mean?
The battery management system has detected that hybrid battery module "B" voltage has dropped below the minimum acceptable threshold. This indicates either severely depleted cells, a cell group failure, or high-resistance connections within module B causing excessive voltage drop under load.
Safety Warning
Do not drive the vehicle. Low module voltage indicates cell failure which can lead to internal short circuits and potential thermal events.
Common Causes
40%
One or more failed cells within module B with reduced capacity causing low voltage
25%
High-resistance bus bar connection at module B causing excessive voltage drop
20%
Cell imbalance within module B where a weak cell drags down overall module voltage
15%
BMS cell balancing failure allowing module B to become deeply discharged
Diagnostic Steps
1
Step 1: Record module B voltage and compare to all other modules via scan tool. A difference greater than 1V from pack average indicates module-level failure.
2
Step 2: Fully charge the battery pack and measure module B voltage at rest. If it remains significantly lower than peers, the module has reduced capacity.
3
Step 3: Measure individual cell voltages within module B. Identify any cell reading below manufacturer minimum threshold (typically 3.0V for lithium).
4
Step 4: Check bus bar connections at module B using a milliohm meter. Connections should be less than 1 milliohm.
5
Step 5: If a weak cell is identified, the module requires replacement. Match replacement module voltage to within 0.1V of pack average.
Estimated Repair Cost
$500 - $5,000
Parts + labor, varies by vehicle and location
The battery management system has detected that hybrid battery module "B" voltage has dropped below the minimum acceptable threshold. This indicates either severely depleted cells, a cell group failure, or high-resistance connections within module B causing excessive voltage drop under load.
The most common cause of P0B29 (Hybrid Battery "B" Voltage Low) is: One or more failed cells within module B with reduced capacity causing low voltage
Typical repair costs for P0B29 range from $500 to $5,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Do not drive the vehicle. Low module voltage indicates cell failure which can lead to internal short circuits and potential thermal events.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0B29 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Battery / High Voltage System
Difficulty
Type
Generic (SAE)
Recommended Tools
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