What it means
The ECU detects an open circuit in the control of fuel volume regulator A (often the metering valve on the high-pressure fuel pump). The actuator does not respond, so rail pressure cannot be controlled accurately.
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 Volume Regulator A controls how much fuel enters the high-pressure fuel system, often through a metering valve on the high-pressure pump. P0001 sets when the engine control module detects an open in the regulator's control circuit, so it may be unable to command fuel delivery and rail pressure correctly.
Common causes
Most likely first.
- Wiring break or unplugged connector
- Regulator solenoid coil open
- ECU output driver failed
Symptoms
- Check engine light on
- Hard starting or no start
- Engine may stall or run poorly
- Reduced power
How to diagnose it
- Read freeze-frame data and scan for related fuel-pressure or regulator codes to see under what conditions the open circuit was detected.
- Inspect the Fuel Volume Regulator A connector for disconnection, loose pins, corrosion, or damage.
- Trace the regulator wiring back toward the control module and look for breaks, chafing, or previous repairs.
- Check regulator command and fuel-rail pressure data during cranking or running, as appropriate, to see whether pressure responds.
- Test circuit continuity and the regulator coil against the manufacturer's specification before considering a control-module output fault.
Common fixes
- Reconnect the Fuel Volume Regulator A connector or repair damaged terminals.
- Repair an open or damaged section of regulator wiring.
- Replace the regulator if its coil fails testing against the manufacturer's specification.
- Repair a confirmed control-module output fault only after the circuit and regulator test correctly.
Can I keep driving?
The engine may be hard to start, stall, or lose power; avoid driving if it will not idle reliably or stalls in traffic. If it runs normally, keep trips short and stop if power drops or the engine begins to stall.
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.