What it means
Open circuit at fuel pressure regulator A. The actuator that controls rail pressure cannot be driven.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
Fuel pressure regulator A is an electrically controlled actuator that helps the system maintain the required fuel pressure. The control module sets P0090 when it detects an open circuit in the regulator A control path, preventing it from commanding the regulator as intended.
Common causes
Most likely first.
- Wiring break or unplugged connector
- Regulator solenoid open
- Pin pushed back out of connector body
Symptoms
- Check engine light on
- Hard start, no start, or stalling under load
- Power loss especially at high load or rpm
- Possible long cranking time
How to diagnose it
- Save freeze-frame data and check whether the fault occurred during starting, under load, or alongside low-pressure or rail-pressure codes.
- Inspect the regulator A connector and harness for an unplugged connector, broken wire, damaged insulation, or a terminal pushed back in the connector body.
- Check the regulator circuit fuse, power, and ground connections using the vehicle wiring diagram.
- Test circuit continuity and check the regulator solenoid for an open winding using the manufacturer's procedure.
- If the wiring and regulator pass, verify the control module output and commanded regulator operation according to the manufacturer's diagnostic procedure.
Common fixes
- Reconnect the regulator A connector and secure the harness.
- Repair a broken control wire or pushed-back connector terminal.
- Restore a failed power or ground connection and address the cause of any blown fuse.
- Replace the regulator A solenoid if testing confirms its winding is open.
- Repair the control module circuit only if the regulator and wiring test correctly.
Can I keep driving?
Avoid driving if the engine is hard to start, stalls, or loses power under load; an uncontrolled fuel-pressure fault can leave you without power in traffic. If it runs normally, keep trips short and arrange prompt diagnosis.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.