ENGINE AND EMISSION CONTROL SYSTEM DESCRIPTION - Idle Speed Control
EF & EC-21flowchartIdle Speed Control
INPUT/OUTPUT SIGNAL LINE
Crank angle sensor
Signal to E.C.C.S. control unitEngine speed
Engine temperature sensor
Signal to E.C.C.S. control unitEngine coolant temperature
Ignition switch
Signal to E.C.C.S. control unitStart signal
Throttle sensor
Signal to E.C.C.S. control unitThrottle valve position / Throttle valve idle position
Neutral switch
Signal to E.C.C.S. control unitGear position neutral
Air conditioner switch
Signal to E.C.C.S. control unitAir conditioner operation
Power steering oil pressure switch
Signal to E.C.C.S. control unitPower steering load signal
Battery
Signal to E.C.C.S. control unitBattery voltage
Vehicle speed sensor
Signal to E.C.C.S. control unitVehicle speed
Load switch
Signal to E.C.C.S. control unitHeadlamp + rear defogger on
A.B.S.
Signal to E.C.C.S. control unitA.B.S. operating (N-CVT vehicles only)
Probable Cause
Corrective Action
E.C.C.S. control unit
A.A.C. valve
Cause
E.C.C.S. control unit
Fix
A.A.C. valve
SYSTEM DESCRIPTION
NOTE
This system automatically controls engine idle speed to a specified level. Idle speed is controlled through fine adjustment of the amount of air which by-passes the throttle valve via A.A.C. valve. The A.A.C. valve repeats ON/OFF operation according to the signal sent from the E.C.U. The crank angle sensor detects the actual engine speed and sends a signal to the E.C.U. The E.C.U. then controls the ON/OFF time of the A.A.C. valve so that engine speed coincides with the target value memorized in ROM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the ROM is determined by taking into consideration various engine conditions, such as warming up and during deceleration, fuel consumption, and engine load (air conditioner, electrical load).