Evaluate Possible Causes

Loss of Prime

(only applies to stems with pump inlet above level of hydraulic fluid in reservoir)

Does running the pump generate any pressure?

Failed check valve on output of truck-side PTO pump

Failed Check Valve
The quickest way to help identify a failed check valve is to operate the emergency DC back-up pump. If the truck-side check valve has failed, the emergency DC pump will likely not be able to generate enough flow to actuate the hydraulic equipment. When in doubt, remove and examine the check valve for damage

Failed pump in SmartPTO

Pump failure
Pump failure is typically identified through process of elimination, by the presence excessive noise, or by reviewing the telematics data leading up to pump failure. If excessive noise is present after enabling the pump, the pump may have failed. If no other cause can be identified (failed check valve, pressure relief valve, loss of prime, failed spline shaft/coupler, etc), it may be assumed that the pump has failed. Review the telematics data before and after the problem occurred and try to get as much information from the user as possible. Sudden loss of pressure and hydraulic functionality while operating the system is indicative of a pump failure.

Failed pressure relief valve in SmartPTO

Pressure relief valve
The pressure relief valve can be tested to ensure proper crackign pressure, but it is easy enough to just replace the pressure reliefe valve (Viatec PN: 45.0009.01)

Failed Spline Shaft/Shaft coupler

Failed spline shafts/coupler
Failed spline shafts/coupler is unlikely. If all other possibilities have been ruled out and mechanical failure of the pump, spline, or coupler are the only remaining options, remove the pump following the procedure defined in the “Pump Swap Guide” (available on request) and inspect the splines of the pump and motor and ensuring that they have not broken or worn down to the point of failure. Inspect the haft coupler to ensure that the internal splines haven’t failed and the coupler body is intact.

Other failed hydraulic valve in truck-side system

Check any other valves that could create a leak path back to the hydraulic fluid tank.