P3804high severityPowertrain
48V System Isolation Fault
on 2021 Audi A6 3.0L Turbo V6 · AWD
What this code means
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.
Other Powertrain codes on this vehicle
P0001
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P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1