P0B5C

What it means

P0B5C means the hybrid or EV battery control unit saw a signal that was too high on the voltage sense circuit labelled 'G'. This is usually a reading above the expected range, or a circuit voltage that suggests a short to voltage or an open circuit. Which cell block or module 'G' refers to depends on the model and pack layout, so check the manufacturer's data.

Symptoms

• Hybrid or EV system warning light on the dashboard, plus the engine management light
• Reduced power or limp mode
• Car refusing to go into Ready mode, or shutting down the hybrid system while driving
• Poor fuel economy, with the engine running more often than normal on a hybrid
• Reduced electric range or an erratic state of charge reading
• Cooling fan for the battery pack running harder than normal

Possible causes

• Damaged, corroded or loose connector or terminal on the battery voltage sense wiringlikely
• Open circuit or high resistance in the sense wire, giving a false high readinglikely
• Sense wire shorted to a voltage source, or harness damagepossible
• Fault in the battery monitoring or control module's voltage sensing circuitpossible
• Genuine cell block or module imbalance or over-voltage in the traction batterypossible
• Outdated control unit software where the manufacturer has documented a known faultrare

How to diagnose

1. Read all stored and pending codes, then record the freeze frame data. Look for other battery voltage sense, battery temperature or insulation codes that point to a shared cause.
2. Check for manufacturer service bulletins and known issues for this model and battery pack.
3. Look at live data and compare the reported voltage for each cell block or module. Note whether block G is a clear outlier or reads implausibly high compared with the rest.
4. Carry out a visual inspection of the accessible low-voltage connectors and harness for damage, corrosion, moisture, heat marks or chafing. Any work near the high-voltage battery must follow the manufacturer's isolation procedure and be done by a technician trained in high-voltage systems.
5. With the system safely isolated, test the sense circuit for continuity, short to voltage and short to earth against the wiring diagram.
6. Check the supply and reference voltages to the battery monitoring module, along with its earth connections.
7. If the wiring is sound, verify the true voltage of the cell block with a suitably rated meter, following the manufacturer's procedure, to separate a sensing fault from a real battery fault.
8. After any repair, clear the code, then road test and confirm that it does not return and that the voltage readings are plausible.

How to fix

• Repair or replace damaged wiring, terminals or connectors in the sense circuit
• Clean or re-seat connectors, and replace any that are corroded or have lost their tension
• Replace the faulty battery monitoring or voltage sensing module if testing shows it is misreading
• Repair or replace the affected battery module or cell block if there is a genuine voltage fault, according to the manufacturer's procedure
• Update the control unit software only if a manufacturer bulletin lists it as the fix for this fault

Can I keep driving?

Nearby codes

• P0B5BGenericHybrid/EV Battery Voltage Sense G Circuit Low
• P0B5DGenericHybrid/EV Battery Voltage Sense G Circuit Intermittent/Erratic