DISC 1028458 - Caterpillar

System Operation Description:Electrical power is supplied to the control module for the Electronic Ignition System (EIS). Electrical power is also supplied to these optional components:
Status Control Module (SCM)
Electronic Control Module (ECM) for the air/fuel ratio control
PWM Converter
Oxygen buffer
Electronic service toolThe EIS control module does not diagnose the power supply. Therefore, the module will not generate a diagnostic code if the power supply is faulty.The SCM will generate a 06 dIAG code if the power supply to the SCM is low or unstable. Refer to Systems Operation, SENR6420 for the procedure for troubleshooting this code.The ECM will generate a 168-02 System Voltage intermittent/erratic if there is a problem with the power supply. The code can be caused by any of these conditions:
The ECM has detected engine rpm during the normal powerup sequence. This will occur if the engine is running and the electrical power is cycled.
The power supply to the ECM is intermittent.
There is a noisy component in the secondary ignition system.The ECM will send a shutdown command to the EIS control module if a 168-02 code is generated. The ignition and the fuel will be shut down.Grounding PracticesProper grounding is necessary for optimum engine performance and reliability. Improper grounding will result in uncontrolled electrical circuit paths and in unreliable electrical circuit paths. Refer to the engine's Operation and Maintenance Manual for additional information on proper grounding practices.Requirements for the Power SupplyThe 24 VDC power supply for the engine can be provided by a battery or by an electrical power supply. The power supply must be capable of providing sufficient current and sufficient voltage in order to start the engine.The batteries and the battery cables must be the correct size in order to minimize voltage drops. This is particularly important during cranking. The supply voltage at the EIS control module must remain above 18 VDC during cranking. Otherwise, the engine may not start. Random diagnostic codes may be generated by the control module.The control module requires an instantaneous current flow of at least 16 amperes at a minimum voltage of 18 VDC in order to power up. The control module requires a continuous current flow of at least 3 amperes at a minimum voltage of 18 VDC for continuous operation. The ECM requires an instantaneous current flow of at least 16 amperes at a minimum voltage of 18 VDC in order to power up. The control module requires a continuous current flow of at least 10 amperes at a minimum voltage of 18 VDC for continuous operation.The wiring from the power supply to the modules must provide a maximum voltage drop of 1.0 VDC.
Illustration 1 g01045468
Schematic diagram