Ignition Switch - Operation

OPERATION

ELECTRONIC IGNITION SWITCH (EIS) OPERATING MODES

The EIS is programmed to adaptively control the on/off state of vehicle electrical systems based on the physical position of the EIS key. There are two main modes of EIS operation, Ignition Switch On, Engine Off, and Engine Start-Up Mode.

Key Lock/Shift Lock

The EIS has a mechanical key lock feature which prevents the FOB with Integrated Key (FOBIK) from being removed from the EIS unless the ignition switch is in the LOCK position. In addition, vehicles with an automatic transmission a shift lock feature, which prevents the FOBIK from being rotated in the ignition switch to the LOCK position unless the transmission shift lever is in the PARK position. The shift lock feature is also part of the Brake Transmission Shift Interlock (BTSI), which prevents the automatic transmission shift lever from being moved out of the PARK position until the ignition switch is unlocked and the brake is applied. A mechanical shift lock cable linkage is connected between the EIS and the automatic transmission shift lever assembly to control this feature.

Ignition Switch On (Engine Off)

When the Electronic Ignition Switch/Central Gateway (EIS/CGW) is turned to the ON position, it will send the ON signal to the ECM through the CAN-C bus. When the diesel ECM receives the ON signal, it will send a signal through the LIN bus to actuate the glow plug module, which provides battery voltage to the glow plugs. At the same time, the diesel ECM actuates the fuel pump relay, which battery voltage to the in-tank (low pressure) fuel pump. If the engine is not started within approximately 4 seconds of the diesel ECM receiving the ON signal from the EIS/CGW, diesel ECM will turn off the in-tank fuel pump.

Engine Start-Up Mode

When the EIS/CGW is turned to the START position from the ON position, it will send the ON and START signals to the ECM through the CAN-C bus. When the ECM receives the ON and START signals, and the Gearshift is in neutral or park, the ECM will actuate the Starter Relay, which provides battery voltage to the Starter Solenoid, which actuates the Starter. As the engine cranks, the ECM will use the signals from the Camshaft and Crankshaft Position Sensors to determine when cylinder 1 is at TDC. When the ECM has sensed engine RPM and the TDC position of cylinder 1, it will sequence the actuation of the injectors according to engine firing order. If the camshaft position sensor is not present during engine cranking, the engine will not start.

EIS Diagnostics

Most problems with the Starting System can be identified with basic conventional diagnostic methods. However, electrical or CAN-C bus faults related to the EIS, ECM will require a scan tool to access the On-Board Diagnostics (OBD) functions of the ECM. The EIS is monitored by the ECM via the CAN-C bus, and may produce a Diagnostic Trouble Code (DTC) depending on the type of fault present. Refer to the appropriate diagnostic procedures for EIS or ECM Drive Authorization System (DAS) related DTCs.