P3657high severityPowertrain
GDI Fuel System Priming Pump Performance
on 2021 Subaru Legacy 2.5L H4 · AWD
What this code means
The low-pressure electric fuel pump that primes the GDI high-pressure fuel system is not delivering adequate fuel volume or pressure to the HP pump inlet.
Symptoms
- Extended cranking time
- Hard start after sitting
- Fuel rail slow to build pressure
- Engine stalling after start
- HP pump cavitation noise
Common causes
- Weak fuel pump motor
- Clogged fuel filter
- Fuel pump check valve leak
- Fuel tank pickup sock restricted
- Fuel pump relay intermittent
Diagnostic steps
- Measure fuel pressure at HP pump inlet
- Test electric fuel pump current draw
- Check fuel filter restriction
- Test fuel pump check valve hold pressure
- Inspect fuel pump relay and wiring
Repair notes
Replace low-pressure fuel pump or fuel filter. GDI systems are sensitive to feed pressure - even slight deficiency causes HP pump issues.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
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