P0B95

What it means

P0B95 is the generic code for a fault in the circuit that senses the voltage of the hybrid or EV traction battery, labelled sense circuit 'S'. The battery control unit compared the voltage signal with what it expected, or with other voltage readings, and found it out of range, implausible or missing. Which part of the pack 'S' refers to depends on the model, so check the manufacturer's information for the vehicle.

Symptoms

• Hybrid system, EV system or general warning light on the dash
• Reduced power or limp-home mode
• Reduced or erratic electric-only range or state-of-charge reading
• Hybrid system will not start or the car will not go into ready mode
• Poor fuel economy because the engine runs more than normal
• Charging slower than normal or stopping early on plug-in models

Possible causes

• Damaged, corroded or loose wiring or connector in the battery voltage sensing circuitlikely
• Fault in the battery monitoring module or battery control unit that reads the voltage signallikely
• Failed internal voltage sensor or cell monitoring circuit within the traction battery packpossible
• Imbalanced or degraded battery cells giving readings that do not agree with each otherpossible
• Low or unstable 12 V auxiliary battery or poor earth affecting the control unitspossible
• Moisture ingress or physical damage to the battery pack or its harnessrare

How to diagnose

1. Read all stored and pending codes and record the freeze frame data, noting battery voltage, state of charge and temperature when the code set.
2. Check for other hybrid or battery codes, as communication, 12 V supply or cell balance codes can point to the real cause.
3. Test the 12 V auxiliary battery and charging, and check its terminals and earths, because low supply can upset the control units.
4. Check for relevant manufacturer service bulletins for the model and battery type.
5. Have a trained technician make the high-voltage system safe following the manufacturer's procedure before any hands-on work on orange cabling or the pack.
6. Inspect the sensing wiring and connectors for chafing, corrosion, water, heat damage or poor pin tension, and look at the pack for damage or leaks.
7. Using live data, compare the reported pack voltage and individual block or cell voltages, looking for one reading that is out of line or stuck.
8. Check the voltage sense circuit for continuity, short circuits and supply or reference values against the manufacturer's data, and clear the code and retest to see if it returns.

How to fix

• Repair or replace damaged wiring and clean or renew faulty connectors in the voltage sense circuit.
• Replace the battery monitoring module or control unit if it is confirmed faulty, following the manufacturer's procedure for coding or setup.
• Repair or replace the affected section or sensor of the traction battery pack, using a trained high-voltage technician.
• Rebalance or replace degraded battery modules or cells if the diagnosis shows they are causing the fault.
• Renew a weak 12 V battery or repair earth faults, then recheck for the code.
• Dry out and repair any water damage, and replace affected components as the manufacturer directs.

Can I keep driving?

Nearby codes

• P0B94GenericHybrid/EV Battery Voltage Sense R Circuit Intermittent/Erratic
• P0B96GenericHybrid/EV Battery Voltage Sense S Circuit Range/Performance