CONTROL FUNCTIONS (CONT’D)

General (Cont’d)

Contact output

There are two schemes for contact output of the E-ECU: high-side output and low-side output. See [Figure 10-40-11] and [See "I/O description" on page 10-20-11] for the details of the Eco-governor E-ECU contact output’s sink/source and allowable current.

In this manual, output transistor ON is referred to as logical "1" and output transistor OFF as logical "0". In the high-side output scheme, the output terminal goes high when the transistor turns off. In the low-side output scheme, the output terminal goes low when the transistor turns off.

Figure 10-40-11

Voltage=High Voltage=Low ECU logic=0ECU logic=1

(a)High-side contact output

Rack actuator output logic=0ECU logic=1

The rack actuator output is a high side output as shown in [Figure 10-40-12].

The E-ECU adjust the magnitude of current flowing through the rack actuator solenoid by shortening or lengthening the ON-duration of the output transistor. The rack position of the fuel injection pump varies depending on the magnitude of current flowing through the rack actuator.

Figure 10-40-12

Voltage=High ECU PWM output 0.4ms Short Long

Voltage=Low ECU Small current Large current

This technique where the ON duration of the transistor is changed to provide current control is called PWM (Pulse Width Modulation).