b'What we normally see is a desired pump value above zero to 750 will resultThe LIN bus looks normal, with a digital signal, the back-up circuit is steady in an actual speed of 750 RPM, which I normally see as the minimum pumpat battery positive volts, and pump current cycles ON at ABOUT 2 amps speed, for an idling engine. Once the desired value is above 750, it willthen settles down to just ABOUT half an amp, before cycling o\x1e.match the actual pump speed. Its important to remember this, because I get a lot of questions about pumps running faster than desired at idle, and this is a normal condition.If the pump data displays an RPM of 5,000, the LIN bus might have a fault. As this is the emergency pump speed. If the emergency circuit has a fault, the ECM can still control pump speed. A fault code will be set (301C00 Emergency run switch failure.). Emergency operations will not work.Using a scope in conjunction with our iSCAN diagnostic software, we can monitor speed and the pump circuit to test electrical function of the pump.Before digging too deep, its always smart to check for fault codes. This vehicle has a communication fault code stored That gives us direction as-well as con\x1frmation that our circuit tests are needed.Once engine temperature reaches 180 degrees, the pump is cycled ON at 750 RPM and current is steady at just ABOUT half an amp.To test the circuit I have my scope connected to the LIN bus on channel 1.Pump battery positive measuring current on channel 2.And the back-up circuit on channel 3.LetsinduceashortontheLINbusandseewhathappenswithpump control. After about 15 seconds, pump speed reaches about 5,000 RPM and maxes out. Pump current draw reaches 22 amps.Idling the engine we can see the pump cycle in the data PID when the engine temp is about 176 degrees. Lets zoom in on the data and see whats happening on the circuit.With these known values, you can con\x1frm you have good communication on the LIN bus, con\x1frm the back-up control signal is present, and con\x1frm coolantpumpingusingcurrentdraw.Remembertoalwaysbeginwith basic circuit tests for power and ground.24'