Controller shows E04 and prevents start; engine may have shut down previously under load.

Safety: Allow engine to cool. Do not bypass oil pressure protection; running with low oil pressure can destroy the engine.

• Check oil level: Use the dipstick on the JCB engine. Top up with the correct grade oil to the full mark. Inspect for external leaks around the sump, filter, and rocker cover.
• Inspect oil filter: Ensure the oil filter is tight and not leaking. If recently serviced, verify the correct filter was installed and the old gasket was removed.
• Test oil pressure switch: Locate the oil pressure switch/sensor on the engine block. Check the connector for corrosion. With a multimeter, verify the switch changes state between engine off and cranking (or use a mechanical gauge to confirm actual pressure).
• Check wiring to controller: Trace the oil pressure signal wire to the JCB controller input. Repair any damaged or oil‑soaked connectors.
• If true low pressure: If a mechanical gauge confirms low pressure, do not run the engine. Contact a qualified technician to inspect the oil pump, pickup strainer, and internal bearings.