Power and Grounding Considerations 4.4 Sensor Common Connections Certain components that interface directly with the ECU are connected to the dedicated sensor returns at the P1/J1 customer connector. Separate sensor returns are provided for analog and digital signals. 4.4.1 Digital Sensor Return P1/J1 Pin 5 should only be connected to the ground side of the coolant level sensor and/or the engine retarder (see section 10.1.3 for C15 ACERT and C18 ACERT engines or section 10.2.4 for C7 ACERT and C9 ACERT engines). 4.4.2 Analog Sensor Return P1/J1 Pin 3 should only be connected to the ground side of the auxiliary pressure and auxiliary temperature sensors. NOTE:
Do not connect the Throttle Position Sensor (TPS) ground to either the analog or digital sensor return. 4.5 Suppression of Voltage Transients NOTE: The installation of transient suppression at the source of the transient is required. Caterpillar follows a stringent electrical environment standard that is similar to SAE recommended practices. The use of inductive devices such as relays and solenoids can result in the generation of voltage transients in electrical circuits. Voltage transients that are not suppressed can exceed SAE specifications and lead to the degradation of the performance of the electronic control system. Figure 2:
Voltage Suppression Diagram Power (+) Power (+) Power (+) Power (+) Power (-) Power (-) Power (-) Power (-) The customer should specify relays and solenoids with built-in voltage transient suppression. Refer to Figure 2 for ways to minimize voltage transients from relays and solenoids without built-in voltage transient suppression. Techniques include the installation of a diode or resistor of the proper size in parallel with the solenoid or the relay coil. A P P L I C A T I O N A N D I N S T A L L A T I O N G U I D E 23