PUMP GP-GEAR 6P7788 - Caterpillar

Table 1
Diagnostic Codes Table    
Code and Description    Conditions which Generate this Code    System Response    
3256-5 Water Pump Output: Current Low     The current to the Electric Water Pump (EWP) is low.     The code is logged.    
The Power Train Electric Drive System and the Accessory Power System will contain hazardous voltage levels during machine operation and for a period of time after machine shutdown.Do not remove any covers that will expose energized electrical components while the engine is operating. Do not remove any covers that will expose the energized electrical components while the components remain energized following an engine shutdown.Do not perform any type of electrical maintenance on the orange hazardous voltage conductors, the power train components or the accessory power system components while the engine is operating.Do not perform any type of electrical maintenance on the orange hazardous voltage conductors, the power train components or the accessory power system components while the components remain energized following an engine shutdown.Always perform the safe shutdown and de-energizing procedure before performing electrical service on the Power Train Electric Drive System or the Accessory Power System.Failure to follow these instructions could result in personal injury or death.
In order to avoid the build up of hazardous live voltages on the exposed surfaces, all grounding wires must be properly connected at all times during engine operation.Any disconnected grounding wires (including the grounding bond wires, the conductor shield wires, the power inverter grounding straps and the component housing grounding straps) must be properly reconnected before the engine is started.Failure to follow these instructions could result in personal injury or death.
Note: Always perform the procedure for safe shutdown and de-energizing before performing electrical service on the Power Train Electric Drive System or the Accessory Power System. This procedure must be performed in order to verify that the voltage in the power train electrical system has been discharged to less than 50.0 VDC. Refer to the Specifications, Systems Operation, Troubleshooting, Testing and Adjusting, "Electrical Maintenance Guidlines" for the proper procedure.Note: A multimeter must be used to verify that there is little or no voltage present at the exposed conductors before any other action is taken. The voltage must be manually measured in order to confirm it to be at a low level (50.0 VDC or less).Test Step 1. Determine the Diagnostic Code
Establish communication between the Caterpillar Electric Technician (ET) and the Electronic Control Module (ECM). Refer to Troubleshooting, "Electronic Service Tools", if necessary.
Determine the diagnostic code(s) that are active.Note: Check for codes that pertain to the water pump circuit. Troubleshoot any codes before proceding with this procedure.Results:
A 3256-5 code is active. - Proceed to Test Step 2.Test Step 2. Low Pump Module Output Current At the EWP
Illustration 1 g02026201
EWPC at the rear of the engine compartment on the upper right side (1) EWPC (2) 320 VDC accessory power bus supply from the APC (3) Four conductor, three-phase, AC supply conductor cable to the electric water pump (4) System power and control circuit