P0B50

What it means

P0B50 is a generic powertrain code meaning the hybrid or EV battery control unit has found the signal from voltage sense circuit 'E' to be out of range or implausible. It usually sets when the measured voltage for that sensing point does not agree with the other voltage sensors, with the expected pack voltage, or with the values it should be able to reach. Which cell group or sensing point 'E' refers to depends on the vehicle and battery design.

Symptoms

• Hybrid system or battery warning light on
• Malfunction indicator lamp on
• Reduced power or limp-home mode
• Reduced or no electric assist or EV range
• Hybrid system refusing to start or ready light not appearing
• Unusual battery charge level readings or erratic state of charge display

Possible causes

• Loose, corroded or damaged connector or terminal at the voltage sense circuit or battery control unitlikely
• Damaged, chafed or open or shorted wiring in the voltage sense harnesslikely
• Faulty cell monitoring circuit or voltage sensor within the battery pack or monitoring modulepossible
• Imbalanced or degraded battery cells or modules causing implausible readingspossible
• Poor busbar or high-voltage connection tightness affecting the measured voltagepossible
• Fault in the battery control unit itself or outdated softwarerare
• Moisture or coolant ingress into the battery pack or monitoring electronicsrare

How to diagnose

1. Read all stored and pending codes and note any other battery voltage, temperature, insulation or communication faults, as these can point to the same root cause.
2. Read freeze frame data and record pack voltage, state of charge, temperatures and the conditions when the code set.
3. Check for manufacturer service bulletins and software updates relevant to the model and battery type.
4. Carry out a visual inspection of accessible low-voltage connectors and harness for damage, corrosion, moisture or heat marks. Only qualified staff trained in high-voltage safety should go near the battery pack or orange cables.
5. Using live data, compare the individual cell or block voltages and look for one reading that is out of line or stuck, noting that the layout depends on the model.
6. Check the 12 V battery condition and charging voltage, as low supply voltage can upset the monitoring electronics.
7. Following the manufacturer procedure and with the high-voltage system safely isolated by a qualified person, test the sense circuit for continuity, shorts and resistance and check connection tightness.
8. Clear the code and road test, then recheck live data to see whether the fault returns.

How to fix

• Repair or replace damaged wiring and clean or replace faulty connectors and terminals in the sense circuit.
• Replace a faulty cell monitoring module or voltage sensing component where the diagnosis confirms it.
• Rebalance, repair or replace degraded battery modules or the pack as directed by the manufacturer procedure.
• Retighten or repair high-voltage busbar connections to the specified torque.
• Update the battery control unit software only if a known fault is covered by an official update, or replace the unit if proven faulty.
• Dry out and repair any moisture ingress and fix its source.

Can I keep driving?

Nearby codes

• P0B4FGenericHybrid/EV Battery Voltage Sense E Circuit
• P0B51GenericHybrid/EV Battery Voltage Sense E Circuit Low