P0B88

What it means

P0B88 means the hybrid or EV battery control unit has seen the signal from the battery voltage sense circuit labelled 'P' reading lower than expected. The control unit compares this reading with its limits and with other voltage measurements. Which part of the pack the 'P' circuit monitors, and how the sensing is arranged, depends on the model and battery design.

Symptoms

• Hybrid or EV system warning light, or malfunction indicator lamp, on
• Reduced power or limp-home mode
• Reduced or erratic electric-only driving and regenerative braking
• Poor or unstable battery state-of-charge reading
• Car slow to enter ready mode or refusing to ready
• Poor fuel economy or reduced EV range

Possible causes

• Damaged, chafed or corroded wiring in the battery voltage sense circuit (open circuit, high resistance or short to ground)likely
• Loose, corroded or contaminated connector at the battery monitoring unit or battery packlikely
• Faulty battery monitoring or voltage sensing module/boardpossible
• Genuinely low voltage in part of the battery pack caused by a weak or failed cell or modulepossible
• Water ingress or coolant/condensation contamination affecting the sense circuitpossible
• Battery control unit fault or outdated software, where the manufacturer has identified this as a known issuerare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting battery voltages, state of charge, temperature and whether other battery voltage or cell-balance codes are present
2. Check for technical service bulletins or known issues for the specific model and battery type, as the 'P' circuit layout varies
3. Visually inspect accessible wiring, connectors and the battery pack surround for damage, corrosion, water or impact marks, without touching high-voltage components unless qualified
4. Using live data, compare the voltage readings from the sensing circuits with each other and with the total pack voltage to see whether the low reading is real or a sensing fault
5. Isolate the high-voltage system following the manufacturer's procedure, then, if qualified, check the sense circuit for continuity, resistance and shorts to ground against the wiring diagram
6. Check the low-voltage supply, earths and battery condition, because poor supply can cause false readings
7. Clear the code and road test or cycle the system to see if it returns, and confirm whether the fault is constant or intermittent
8. If the circuit is sound, test individual cell or module voltages and the monitoring module following the manufacturer's procedure

How to fix

• Repair or replace damaged wiring and clean or replace corroded or loose connectors in the sense circuit
• Dry out and treat any water ingress, and cure its source before refitting parts
• Replace the faulty battery monitoring or voltage sensing module if testing proves it defective
• Repair or replace the weak battery module or pack section if it is truly low in voltage, following the manufacturer's procedure
• Update the control unit software only if the manufacturer lists an outdated calibration as a known cause for this fault

Can I keep driving?

Nearby codes

• P0B87GenericHybrid/EV Battery Voltage Sense P Circuit Range/Performance
• P0B89GenericHybrid/EV Battery Voltage Sense P Circuit High