P3656moderate severityPowertrain
Port and Direct Injection System Imbalance
on 2015 Audi A8 3.0L Supercharged V6 · AWD
What this code means
In dual-injection systems (combined port and direct injection), the balance between PFI and GDI fueling is incorrect.
Symptoms
- Check Engine Light
- Rough idle
- Knock or ping under load
- Poor emissions
- Fuel economy reduced
- Cold start misfires
Common causes
- Port injector partial blockage
- GDI injector drift
- Fuel pressure imbalance between systems
- PCM fuel strategy calibration error
- Intake runner flap affecting port injection
Diagnostic steps
- Compare port vs direct injection fuel trim data
- Test individual port injector flow
- Test GDI injector flow rates
- Monitor knock sensor activity
- Check intake runner valve operation
Repair notes
Clean or replace affected injectors. Recalibrate fuel split strategy if software update is available. Check intake runner valves.
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