48V System Isolation Fault
2012-2019 Fiat 500 1.4L I4
Description
The 48V electrical system isolation monitoring has detected reduced insulation resistance between the 48V bus and vehicle chassis.
Symptoms
- 48V system may be disabled
- Mild hybrid functions lost
- Warning indicator illuminated
- Potential electrical shock risk
- System enters safe mode
Common Causes
- Moisture in 48V connector
- Damaged 48V cable insulation
- 48V battery case leak
- Component insulation breakdown
- Wiring chafed against chassis
Diagnostic Steps
- Read 48V isolation resistance value
- Perform 48V isolation test per segment
- Inspect 48V wiring for damage
- Check 48V connectors for moisture
- Test 48V battery case integrity
Repair Notes
Locate and repair source of isolation loss. While 48V is below lethal threshold, it can cause burns and arcing. Repair promptly.
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
P3804 on Other Vehicles
Fiat 124 Spider
2017-2020 1.4L I4 Turbo
Fiat 500 Abarth
2012-2019 1.4L I4 Turbo
Fiat 500 BR
2011-2020 1.4L I4 Flex Fire Evo
Fiat 500 PL
2007-2025 1.0L I3 Hybrid FireFly 70
Fiat 500 PL
2007-2025 1.2L I4 Fire 69
Fiat 500L
2014-2020 1.4L I4 Turbo
Fiat 500X
2016-2024 1.4L I4 Turbo
Fiat Argo
2017-2025 1.0L I4 Flex Firefly
Common Questions
What does code P3804 mean on a 2012-2019 Fiat 500?
P3804 stands for "48V System Isolation Fault". The 48V electrical system isolation monitoring has detected reduced insulation resistance between the 48V bus and vehicle chassis.
What are the symptoms of P3804 on a Fiat 500?
Common symptoms of P3804 include: 48V system may be disabled, Mild hybrid functions lost, Warning indicator illuminated, Potential electrical shock risk, System enters safe mode.
What causes P3804 on a 2012-2019 Fiat 500?
Common causes of P3804 include: Moisture in 48V connector, Damaged 48V cable insulation, 48V battery case leak, Component insulation breakdown, Wiring chafed against chassis.