MI-04 Electronic Throttle Conventional throttle systems rely on mechanical linkage to control the throttle valve. To meet fluctuating engine demands a conventional system will typically include throttle valve actuators designed to readjust the throttle valve opening in response to engine demand, together with idle control actuators or idle air bypass valves. In contrast, the MI-04 system uses electronic throttle control (ETC). The SECM controls the throttle valve based on engine RPM, engine load, and information received from the Acceleration Pedal. Two mutually opposed potentiometers on the Acceleration Pedal assembly monitor accelerator pedal travel.
The electronic throttle used in the MI-04 system is a Bosch 32mm Electronic Throttle Body DV-E5 (Figure 20). The DV-E5 is a single unit assembly, which includes the throttle valve, throttle-valve actuator (DC motor) and the throttle position sensor (TPS) (Figure 21). The SECM calculates the correct throttle valve opening that corresponds to the driver’s demand, makes any adjustments needed for adaptation to the engine’s current operating conditions and then generates a corresponding electrical (driver) signal to the throttle-valve actuator. There are multiple limp-home modes available with ETC. 1.
If the throttle itself is suspected of being inoperable, the SECM will remove the power to the throttle motor. When the power is removed, the throttle blade returns to its “default” position, approximately 7% open. 2. If the SECM can still control the throttle but some other part of the system is suspected of failure, the SECM will enter a “Reduced Power” mode. In this mode, the power output of the engine is limited by reducing the maximum throttle position allowed. 3. In some cases, the SECM will shut the engine down. This is accomplished by stopping ignition, turning off the fuel, and disabling the throttle.
In place of a dual TPS design (TPS1 and TPS2), the SECM calculates correct throttle position (Predicted TPS) based on RPM and MAP and compares this to the actual throttle position, based on TPS1. The SECM continuously checks and monitors all sensors and calculations that effect throttle valve position whenever the engine is running. If any malfunctions are encountered, the SECM’s initial response is to revert to redundant sensors and calculated data. If no redundant signal is available or calculated data cannot solve the malfunction, the SECM will drive the system into one of it’s limp-home modes or shut the engine down, storing the appropriate fault information in the SECM.
Figure 20 Throttle Plate Gear Drive DC Drive Motor Bosch 32mm Electronic Throttle Body DV-E5 Picture courtesy of Robert Bosch GmbH Figure 21 G420E/G424E Tier LP Engine System Operational Overview 22