SWITCH AS-LIQUID LEVEL 3246499 - Caterpillar

System OperationThe Electronic Control Module (ECM) supplies a regulated voltage of 5.0 0.2 VDC to the sensors.The supply voltage for the sensors is routed from the ECM to terminal 1 of each sensor connector. The sensor return for the sensors is routed from the ECM to terminal 2 of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If any of the diagnostic codes are active, a sensor may have been damaged. Repair the sensor supply and check for any active sensor diagnostic codes in order to determine if a sensor has been damaged.
Illustration 1 g01240891
Sensor connector (1) 5 V or 8 V sensor supply (2) Sensor return (3) Signal
Table 2
Sensor Supply     Sensor Supply ECM Location    
Sensor Supply #1     Sensors on A4:E4 engine ECM J2 connector or A5:E2 aftertreatment controller J2 connector    
Sensor Supply #2     Sensors on A4:E4 engine ECM J1 connector    
Illustration 2 g03390008
Note: The diagram above is a simplified schematic of the ECM - relay circuit. The schematic is electrically correct. However, not all of the possible sensors or harness connectors are shown. Refer to the latest revision of the Electrical Schematic for the complete schematic for your application.Complete the procedure in the order in which the steps are listed.
Table 3
Troubleshooting Test Steps     Values     Results    
1. Determine the Code
A. Connect Cat® ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Turn the keyswitch