P0BB6

What it means

P0BB6 means the control unit monitoring the hybrid or EV traction battery has seen a signal from one of its battery voltage sense circuits (identified as 'Y') that is higher than the expected range. This points to a problem in the sensing circuit or the sensing module rather than proving the battery itself is overcharged. Which circuit or voltage channel 'Y' refers to depends on the vehicle and battery design.

Symptoms

• Hybrid system or EV warning light on, often with the main malfunction light
• Reduced power or limp mode
• Reduced or no electric assist or electric-only driving
• Inaccurate or erratic battery state-of-charge reading
• Engine running more often than normal on a hybrid
• Vehicle refusing to enter ready mode or shutting down (in some cases)

Possible causes

• Damaged, corroded or loose connector or wiring in the battery voltage sense circuit (short to voltage or high resistance fault)likely
• Faulty battery voltage sensor or battery monitoring or control module giving a false high readinglikely
• Poor supply or earth to the battery monitoring module, or a reference voltage faultpossible
• Cell sensing harness fault inside the battery pack, such as a damaged sense lead or poor contact at a busbarpossible
• Genuine over-voltage in part of the traction battery, such as an imbalanced or failing cell grouppossible
• Outdated or faulty software in the battery or hybrid control module, where the manufacturer has identified this as a known causerare

How to diagnose

1. Read all stored and pending codes and record the freeze frame data; note any other battery, isolation or communication codes, as these help narrow down the fault.
2. Check for manufacturer service bulletins and software updates relevant to the model and the code, and find out which circuit 'Y' refers to for that vehicle.
3. Visually inspect the low-voltage wiring and connectors to the battery monitoring module and sensors for damage, water ingress, corrosion, chafing or pushed-back pins. Do not touch orange high-voltage cables or components unless you are trained and qualified.
4. Check the 12 V battery condition and charging voltage, as low or unstable system voltage can cause false sensing faults.
5. Using live data, compare the reported voltage on the affected channel with the other channels and the total pack voltage; look for a value that is stuck, implausible or out of line.
6. Have a qualified high-voltage technician follow the manufacturer's safe shutdown procedure, then test the sense circuit supply, earth, signal and wiring continuity against the wiring diagram.
7. If the wiring and module supplies are good, have the traction battery checked for cell or module imbalance using the manufacturer's test procedure.
8. After repair, clear the code, run a drive cycle and confirm that the code does not return and the voltage readings are plausible.

How to fix

• Repair or replace damaged wiring, terminals or connectors in the voltage sense circuit.
• Replace a faulty battery voltage sensor or battery monitoring module, then complete any required setup or learning procedure.
• Restore correct supply and earth to the monitoring module.
• Repair or replace the faulty cell sensing harness or busbar connection within the traction battery, by a qualified technician.
• Rebalance, repair or replace the affected battery modules if a genuine cell voltage problem is confirmed.
• Update the control module software if the manufacturer lists an outdated calibration as the cause.

Can I keep driving?

Nearby codes

• P0BB5GenericHybrid/EV Battery Voltage Sense Y Circuit Low
• P0BB7GenericHybrid/EV Battery Voltage Sense Y Circuit Intermittent/Erratic