IMPELLER 4W0251 - Caterpillar

Service Switches
During troubleshooting, it is necessary for the service person to use the diagnostic operations of Caterpillar Monitoring System. Service personnel use the service switches in order to access the different display modes of diagnostic operation. The switches are the momentary type of switch. The service personnel activate the switches by pressing and holding. Pressing the clear switch grounds the clear input (contact 33) of the monitor. Pressing the set switch grounds the set input (contact 23) of the monitor. The location of the service switches will vary depending on the engine that is being serviced. 4C-8195 Control Service Tool
Illustration 1 g00429878
4C-8195 Control Service Tool (1) Mode switch. (2) Clear switch. (3) Scroll switch.The 4C-8195 Control Service Tool is helpful for the service person to make the proper electrical connections at the service connector during troubleshooting. Three connectors are wired in parallel so that the service tool is usable on the different types of machine harnesses.Actuating the mode switch scrolls through the display modes. Actuating the scroll switch will scroll through the display while the main display module is in the service mode or the numeric readout mode. Actuating the clear switch clears the fault that is being continuously shown when the main display module is in service mode. Actuating the clear switch clears all extreme values when the main display module is in tattletale mode.Changing Modes
Table 1
Activation Of Display Operations (Quick Reference)    
Display Operation    Service Contact (1)    Clear Contact (1)    
Changing Modes:    
To Scroll     Ground     Ground    
To Hold     Open     Open    
Harness Code Mode:    
To Scroll     N/A     N/A    
To Hold     Open     Open    
Service Modes:    
To Scroll     Ground     Open    
To Hold     Open (2)     Open    
To Clear (3)     Open     Ground    
Tattletale Mode:    
To Scroll     Ground     Open    
To Hold     Open     Open    
To Clear     Open     Ground    
Numeric Readout Mode:    
To Scroll     Ground     Open    
To Hold     Open     Open    
( 1 ) Of the main display module connector.
( 2 ) Open when the desired information is shown during scrolling.
( 3 ) A diagnostic code can be cleared only while it is on hold. The diagnostic code for a fault that is currently present can not be cleared. Available on applications with digital tattletale mode.For a detailed explanation of the different modes, see Systems Operation, "Modes of Operation".