P0B87
Hybrid/EV Battery Voltage Sense P Circuit Range/Performance.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- B
- AreaHybrid propulsion
- 87
- FaultThe specific fault in that area
What it means
P0B87 means the hybrid or EV battery control unit has found that one of its battery voltage sense circuits, labelled 'P' in the definition, is reading outside the expected range or does not agree with other voltage measurements. The control unit compares the sensed voltage with the pack total, neighbouring sense channels or its own plausibility limits, and it set the code when they did not match. Which sense circuit 'P' refers to depends on the model and battery design, so check the manufacturer data for your vehicle.
Symptoms
- Hybrid or EV system warning light, or a master warning light, on the dashboard
- Reduced power or limp-home mode
- Lower electric-only range, or the engine running more than normal on a hybrid
- Battery state-of-charge display jumping or looking wrong
- Reduced or no charging, or charging stopping early
- Car refusing to go into Ready mode in some cases
Possible causes
- Poor connection, corrosion or a loose terminal at the battery voltage sense wiring or connectorlikely
- Damaged, chafed or open-circuit sense wiring between the battery cells or modules and the battery control unitlikely
- Imbalanced or weak battery cell or module giving a voltage that is genuinely out of rangepossible
- Fault in the battery monitoring or control unit's voltage measurement circuitpossible
- Moisture or coolant ingress, or contamination inside the battery pack or its connectorspossible
- Outdated control unit software where the manufacturer has issued a fix for this faultrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, and note any other battery, cell balance or insulation codes alongside P0B87.
- Check the manufacturer's information for what the 'P' sense circuit refers to on this model, and for any service bulletins or software updates.
- Compare the live voltage of individual cells or modules and the total pack voltage with the data from the battery control unit, looking for one reading that is out of line.
- Visually inspect the accessible battery wiring, connectors and the pack's surroundings for damage, corrosion, moisture or signs of heat.
- Only if you are trained and qualified, and with the high-voltage system isolated by the correct procedure, check the sense circuit for continuity, resistance and insulation.
- Check the battery cooling and ventilation path for blockages that could cause uneven cell temperatures and voltages.
- Clear the code and road test, then recheck the data to see whether the fault returns and under what load or temperature.
How to fix
- Repair or replace damaged sense wiring and clean or replace corroded or loose connectors.
- Rebalance or replace the faulty cell, module or battery section, following the manufacturer's procedure.
- Dry out and repair any moisture ingress and fix the cause of the leak.
- Replace the battery control unit if the voltage measurement circuit is proven faulty, and program it as required.
- Apply the latest manufacturer software update if an outdated calibration is a known cause for this vehicle.
Can I keep driving?
If the car drives normally you can usually continue short, careful journeys to get it checked soon, but expect reduced power or a possible shutdown. Stop and seek help if you see multiple warnings, smell burning or see smoke, or if the car loses drive. High-voltage work must only be done by trained technicians.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.