JCB fault codes — the full list

A fault code records what the controller measured, not what is broken. A low fuel-rail-pressure code is raised by the ECU seeing pressure below target — the cause might be a failing pump, a blocked filter, a leaking injector return, air in the fuel, or the sensor itself lying. The code narrows the search; it does not end it.

Two practical consequences. First, clear the code and reproduce the fault before replacing anything, because an intermittent code and a hard failure need different work. Second, check the cheap and common causes in order — filters, connectors, earths and looms account for more of these than component failure does, and a corroded pin will raise the same code as a dead sensor.

This list is a reference. It is not a repair manual for your machine, and it does not replace the manufacturer’s diagnostic procedure or the torque, pressure and safety figures in it.