APU fuel valve warning on EICAS and fault light on overhead with APU off.
This warning is shown when the commanded position of the fuel shutoff valve does not match the actual valve position. There would be similar warnings for the APU Fuel Isolation Valve also.
The valve is located in the left forward wing root.
9.9 times out of 10...... the valve is going to be the faulty component, but just to make sure I checked for coil voltage at relay K192 and jumped the relay control wires at the actuator plug.
No voltage at relay and the jumper caused the fault to clear...... obvious bad valve (either the internal switch was failed or the valve was not actually moving. In this case, the valve was stuck open.)
Two drawings of system indication. A explanation of internal actuator switch functions can be found here.