P0DE6

What it means

P0DE6 means the hybrid or EV battery control unit has detected that the voltage of at least one cell, or cell group, in the high-voltage battery pack has dropped below the minimum allowed. The battery management system sets it from its cell monitoring circuits when a cell reads below the calibrated threshold, either on load or at rest. The exact number of cells monitored and the threshold depend on the vehicle and battery chemistry.

Symptoms

• Hybrid or EV system warning light, or malfunction indicator lamp, on
• Reduced power or limp-home mode
• Reduced electric range or rapidly falling state of charge
• Engine running more often than normal on a hybrid, or poor fuel economy
• Charging stops early, will not charge fully, or the car will not enter ready mode

Possible causes

• Weak or degraded cell or module in the high-voltage battery pack, with low capacity or high internal resistancelikely
• Imbalance between cells caused by age, long periods of storage or repeated deep dischargelikely
• Fault in the cell voltage sensing circuit, such as a loose or corroded sense lead or connector, or a faulty monitoring boardpossible
• Pack cooling problem (blocked intake, failed fan or duct) causing heat stress and uneven cell ageingpossible
• Internal short or leakage in a cell or modulerare
• Outdated or faulty battery management software, where the manufacturer has identified this as a known cause for the modelrare

How to diagnose

1. Read all stored and pending codes plus freeze frame data. Note state of charge, pack voltage, temperature and load when the code set, and look for other battery, cooling or isolation codes.
2. Check for relevant technical service information or software updates for the specific model and battery type.
3. Visually inspect the 12 V battery, the battery cooling intake and ducts, and the cooling fan for blockage, damage or debris.
4. Using live data, compare individual cell or module voltages at rest and under load, and note which cell or group is low and how far it deviates from the others.
5. Check battery temperature sensor readings and cooling fan operation for plausibility and uneven temperatures across the pack.
6. Have a trained high-voltage technician isolate the system following the manufacturer's safe procedure, then inspect the sense wiring and connectors at the pack and monitoring unit for corrosion, looseness or damage.
7. If one cell group is consistently low, perform a manufacturer-approved pack capacity or balance test to separate a weak cell from a sensing fault.
8. After repair, clear the code and road test, rechecking cell voltages under load.

How to fix

• Repair or replace the damaged module, cell group or battery pack, as the manufacturer's procedure allows.
• Carry out a manufacturer-approved cell balancing or reconditioning procedure if the fault is only imbalance.
• Repair or replace faulty sense leads, connectors or the battery monitoring board.
• Clear the cooling intake and ducts, and replace any failed fan or temperature sensor.
• Update the battery management software only if the manufacturer lists this as the fix for this fault.

Can I keep driving?

Nearby codes

• P0DE5GenericCharge Status Indicator B Control Circuit/Open
• P0DE7GenericHybrid/EV Battery Pack Cell Voltage High