Fault-code directory · ECU and electrical assessment
A difficult start or pressure-control warning can lead straight to a quotation for a fuel pump. Before that decision, establish whether the controller is reporting an electrical fault in a metering or regulating circuit, or whether the fuel system genuinely cannot achieve the requested pressure.
Codes covered
P0001 · P0002 · P0003 · P0004 · P0090 · P0091 · P0092
P0001–P0004 concern a fuel-volume regulator control circuit. P0090–P0092 concern a fuel-pressure regulator control circuit. The installed system and full description identify the actual component. Circuit-low and circuit-high reports are not the same as low or high measured fuel pressure.
Confirm the full description, suffix and reporting module for your vehicle. These are diagnostic starting points, not a parts replacement list.
Evidence that helps narrow the fault
- Preserve commanded and measured pressure, engine speed and battery voltage from the failed start or running event. A low cranking speed can complicate the interpretation.
- Identify the regulating component and its wiring before testing. Modern systems can use several valves, pressure stages and control strategies.
- Inspect connectors and harness routes around the pump and engine. Electrical load and output tests should follow the correct procedure, with appropriate precautions for pressurised fuel.
Choosing the next repair step
A controller repair enquiry is most useful when it includes the valve specification and evidence from the external circuit. An open load, a shorted valve and a pressure-delivery problem are different failures. Do not loosen high-pressure pipes to see whether fuel is present; that does not provide a controlled pressure test and can cause injury.
Will a new fuel-pressure sensor cure a regulator circuit code?
Not necessarily. The sensor reports pressure, while the regulator controls it. The code and circuit identification should establish which part of the system actually needs investigation.
Talk through the fault with AXION
Send the make, model, year, full scan report and a short description of when the fault happens. Include recent repairs or programming attempts. If you do not have a scan, describe the symptoms in your own words.
Workshop assessments are arranged by appointment in Didcot, Oxfordshire. UK-wide postal module testing and remote support are available for suitable work after compatibility and scope are agreed. Please contact us before removing or posting a module.
Assessment options and appointments · Garage and trade support
Related reading
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- Coolant temperature and warm-up faults before changing the thermostat
Reference for generic code terminology: Snap-on diagnostic code reference. Use the manufacturer’s current service information for the actual vehicle and test procedure. This article provides general diagnostic guidance and is not a report of a particular customer repair.