P0B29 on Audi
Hybrid Battery "B" Voltage Low
P0B29 on Audi vehicles indicates hybrid battery "b" voltage low. Au7o has documented this code across 1 Audi model — most commonly on A6 allroad. The battery energy control module monitors every cell block in the high-voltage or 48V battery pack to confirm each is contributing equally. P0B29 sets when the voltage measured across the block designated "B" falls below the calibrated threshold, or falls too far below the other blocks. In practice it means one section of the pack is weak, degraded, or not being sensed correctly - it is a cell-group-level complaint, not a whole-pack complaint.
Common Causes of P0B29
- •Degraded or failing cell block within the battery pack
- •Poor connection at a cell-group busbar or voltage-sense connector
- •Faulty voltage-sense wiring harness inside the pack
- •Failed battery energy control module / cell supervision circuit
- •Battery pack imbalance from long storage or repeated deep discharge
- •On 48V mild-hybrid systems: failing 48V lithium battery or its DC/DC converter
P0B29 on Audi by Model
Audi A6 allroad(1 issue)
- 2020-2024 A6 allroad 48V Battery Low-SoC Protection - Recharge Before Replacement2020-2024
Audi TSB 2067906/5 explains that the 48V battery can enter low-state-of-charge protection and open its internal relays. P0A7D00 can accompany this condition. When measured 48V state of charge is 5%-15%, Audi directs a controlled recharge through the 12V electrical system and says the 48V battery must not be replaced for that condition. P0B2900 alone is also not a reason to replace the battery. This is a guided service procedure, not proof of battery degradation.
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View P0B29 across all makes →Frequently Asked Questions
What does P0B29 mean on Audi?▼
P0B29 stands for "Hybrid Battery "B" Voltage Low." The battery energy control module monitors every cell block in the high-voltage or 48V battery pack to confirm each is contributing equally. P0B29 sets when the voltage measured across the block designated "B" falls below the calibrated threshold, or falls too far below the other blocks. In practice it means one section of the pack is weak, degraded, or not being sensed correctly - it is a cell-group-level complaint, not a whole-pack complaint. On Audi specifically, this code is documented across 1 model.
What causes P0B29 on Audi vehicles?▼
Common causes on Audi: Degraded or failing cell block within the battery pack, Poor connection at a cell-group busbar or voltage-sense connector, Faulty voltage-sense wiring harness inside the pack, Failed battery energy control module / cell supervision circuit, Battery pack imbalance from long storage or repeated deep discharge. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0B29 on a Audi?▼
Repair costs vary widely depending on the root cause and specific Audi model.
Which Audi models have P0B29 documented?▼
Au7o has documented P0B29 on 1 Audi model: A6 allroad.