Operation Modes: Overview

There are seven throttle control modes;
1. Normal
2. Cruise Control
3. Mechanical guard
4. Fixed idle mode
5. Redundancy mode
6. Engine shut-down
7. Full authority

Normal Operating Mode
During normal operation the ECM detects driver throttle pedal input and signals the throttle valve motor to turn the valve to follow the input shaft and mechanical guard. The mechanical and monitoring arrangement of the throttle valve allows the ECM to limit, or reduce, throttle opening to less than driver demand for stability/traction control, or engine power limitation.

Operating Mode
Engine idle speed is controlled by the throttle valve motor varying the blade angle between the restrictions of the mechanical guard (open limit) and the throttle valve motor (closed limit); neither of the mentioned limits are adjustable.

Cruise Control Operating Mode
Engagement of cruise control enables the ECM to calculate and control the required throttle valve opening via the vacuum system. When the driver releases the throttle pedal, the input shaft disengages from the mechanical guard or the vacuum actuator pulls the guard away from the throttle valve. This will cause the throttle pedal to feel light should it be pushed again to accelerate (pressing the pedal further will re-engage the input shaft with the mechanical guard and restore normal feel). With the mechanical guard clear, the necessary throttle valve modulation can be controlled by the ECM which in turn monitors the relative positions, via the previously mentioned sensors, and adjusts the position of the mechanical guard and throttle valve to maintain the set cruise speed.

Operating Mode
Full mechanical operation of the throttle occurs if the ECM detects that a problem has been encountered with a throttle valve position sensor, dc motor, associated harnesses/connectors or the ECM. This is the Mechanical guard mode. In this mode the throttle motor is disengaged thus allowing the throttle valve spring to load the valve against the mechanical guard. The input shaft, mechanical guard and throttle valve are locked together by spring pressure so that the throttle cable is effectively connected directly to the throttle valve. The idle speed will increase in this mode to approximately 1400 rpm and full throttle is available.

Operating Mode
Should a mechanical guard failure occur which indicates that the guard is stuck fully open, Full authority mode will be invoked. The red warning lamp will be lit and road speed will be limited to 120 kph.

Operating Mode
Engine shut-down will occur following multiple failures, such that Mechanical guard mode follows Full authority mode (or vice versa) or the throttle blade sticks.

NOTE: The transition from normal to mechanical guard mode is smoothed by fuel intervention to prevent abnormal loads being applied to the transmission. As engine load is increased fuelling is progressively returned to normal.