48V DC-DC Converter (48V to 12V) Fault
2014-2021 Mazda Mazda6 2.5L I4
Description
The DC-DC converter that steps down 48V to charge the 12V system and battery has a fault. In 48V systems, this converter often replaces the traditional alternator.
Symptoms
- 12V battery not charging
- Electrical accessories dimming
- 12V battery warning light
- Vehicle may not restart
- Multiple low-voltage warnings
- Infotainment resets
Common Causes
- DC-DC converter internal failure
- 48V input voltage out of range
- 12V output regulation failure
- Cooling system issue for converter
- Communication fault with BMS
Diagnostic Steps
- Measure DC-DC converter 12V output
- Check 48V input voltage
- Monitor 12V battery charge state
- Test converter cooling fan
- Read converter internal fault codes
Repair Notes
Replace 48V to 12V DC-DC converter. Charge or replace 12V battery if damaged by undervoltage.
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
P3803 on Other Vehicles
Common Questions
What does code P3803 mean on a 2014-2021 Mazda Mazda6?
P3803 stands for "48V DC-DC Converter (48V to 12V) Fault". The DC-DC converter that steps down 48V to charge the 12V system and battery has a fault. In 48V systems, this converter often replaces the traditional alternator.
What are the symptoms of P3803 on a Mazda Mazda6?
Common symptoms of P3803 include: 12V battery not charging, Electrical accessories dimming, 12V battery warning light, Vehicle may not restart, Multiple low-voltage warnings, Infotainment resets.
What causes P3803 on a 2014-2021 Mazda Mazda6?
Common causes of P3803 include: DC-DC converter internal failure, 48V input voltage out of range, 12V output regulation failure, Cooling system issue for converter, Communication fault with BMS.