Ben was asked to help diagnose a problem on a Komatsu excavator. The back story was that the machine had been looked at previously and parts had been replaced. It had now moved to a level 4 warning where the engine was derated and performance from the machine was seriously downgraded to the point where only a high idle engine speed was possible. A level 4 warning will also trigger a constant sounding alarm as soon as the ignition switches on and with no way of turning it off until the fault is fixed. Follow Ben on his journey to diagnose this machine.