48V Battery State of Charge Low
2019-2024 BMW 3 Series G20 2.0L I4 Turbo B48
Description
The 48V lithium-ion battery state of charge has dropped below the minimum threshold for mild hybrid functions.
Symptoms
- Mild hybrid boost disabled
- Start-stop disabled
- Increased engine load
- Regenerative braking not occurring
- 48V battery warning
- Higher fuel consumption
Common Causes
- 48V battery degradation
- DC-DC converter not charging 48V battery
- Excessive 48V electrical loads
- 48V battery cell imbalance
- Extended vehicle storage without charging
Diagnostic Steps
- Read 48V battery SOC and voltage
- Check 48V DC-DC converter output
- Monitor 48V charging during deceleration
- Test 48V battery health
- Check for excessive 48V parasitic draw
Repair Notes
Allow vehicle to run and recharge 48V battery. If SOC does not recover, test 48V battery and DC-DC converter. Replace if degraded.
Related Codes
Other Powertrain Codes
- P0001Fuel Volume Regulator Control Circuit/Open
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0003Fuel Volume Regulator Control Circuit Low
- P0004Fuel Volume Regulator Control Circuit High
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
- P0011Intake Camshaft Position Timing Over-Advanced Bank 1
- P0012Intake Camshaft Position Timing Over-Retarded Bank 1
- P0013Exhaust Camshaft Position Actuator Circuit/Open Bank 1
- P0014Exhaust Camshaft Position Timing Over-Advanced Bank 1
- P0015Exhaust Camshaft Position Timing Over-Retarded Bank 1
P3801 on Other Vehicles
Common Questions
What does code P3801 mean on a 2019-2024 BMW 3 Series G20?
P3801 stands for "48V Battery State of Charge Low". The 48V lithium-ion battery state of charge has dropped below the minimum threshold for mild hybrid functions.
What are the symptoms of P3801 on a BMW 3 Series G20?
Common symptoms of P3801 include: Mild hybrid boost disabled, Start-stop disabled, Increased engine load, Regenerative braking not occurring, 48V battery warning, Higher fuel consumption.
What causes P3801 on a 2019-2024 BMW 3 Series G20?
Common causes of P3801 include: 48V battery degradation, DC-DC converter not charging 48V battery, Excessive 48V electrical loads, 48V battery cell imbalance, Extended vehicle storage without charging.