Engine Management
Additional Input Checks
Input Additional Strategy Action, Substitute or DefaultValue
Accelerator pedal Accelerator pedal position input 1 compared to If one input fails, the input of the other
position (x 2) and accelerator pedal position input 2. two is used.
mechanical guard Both accelerator pedal position inputs compared to If two inputs fail, ECM adopts fixed
position mechanical guard position input. throttle mode.
Throttle position 1 compared to input 2. If either input fails, ECM adopts
(x 2) Input 1 compared to target value (target value mechanical guard mode of operation.
depends on operating mode, eg. normal running,
cruise control, traction active).
Engine coolant After engine start, checks that expected If fault detected, uses substitute value
temperature temperature increase occurs, then monitors for derived from transmission oil
excessive temperature decrease. temperature.
Mass air flow Compares input with predicted air flow (derived If fault detected, uses throttle angle as
from a map of throttle angle against engine speed). load measurement.
Intake air Monitors for too fast change of input and for fixed If fault detected, uses a fixed intake air
temperature input. temperature of 50˚C (122˚F).
Default Modes
Mode Effect General CHECK Message
Warning ENG
Lamp Lamp (MIL)
Engine shutdown Activates fuel cut-off to stop engine Red On ENGINE FAULT
Fixed throttle Fixed throttle valve angle of approximately 2.5˚ Red On ENGINE FAULT
set, producing maximum engine speed (unloaded)
of approximately 1200 RPM.
Mechanical guard Engine speed increases as throttle valve goes to Red On ENGINE FAULT
mechanical guard position; idle speed increases to
approximately 1400 RPM; full throttle available
Engine speed Engine speed limited to 3000 RPM Amber On ENGINE FAULT
Redundancy Substitute or default value adopted; no noticeable Amber Off ENGINE FAULT
difference in performance
Exhaust emission Substitute or default value adopted; potential None On None
difference in performance
Note: In mechanical guard mode, fuel intervention smooths the transition from normal to default mode, to prevent sudden
acceleration of the vehicle. Also, fuel intervention limits idle speed. Without fuel intervention idle speed would be
approximately 2000 RPM and cause excessive shock loads on the transmission when shifting out of Park or Neutral.
When engine load increases, idle speed fuel intervention is progressively withdrawn.
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