Power Circuitry; Engine Without Stepper Motor Typ E - Toyota COMPUTER-CONTROLLED SYSTEM Training Manual

ELECTRONIC CONTROL SYSTEM - Power Circuitry
POWER CIRCUITRY
This circuitry supplies power to the Engine ECU,
and includes the ignition switch and the EFI main
relay . There are two types of this circuitry in
use . In one, current flows directly from the
ignition switch to the EFI main relay coil to
operate the EFI main relay (the type without the
stepper motor type ISC valve) . In the other, the
Engine ECU operates the EFI main relay directly
ELECTRICAL CIRCUITR Y
EFI fuse
(the type with the stepper motor type ISC Battery
valve) .
1 . ENGINE WITHOUT STEPPER MOTOR
TYPE ISC VALV E
The following diagrams show the type in which
the EFI main relay is operated directly from the
ignition switch . When the ignition switch is
turned on, current flows to the coil of the EFI
main relay, causing the contacts to close . This
supplies power to the +B and +B1 terminals of
the Engine ECU . Battery voltage is supplied at
all times to the BATT terminal of the Engine ECU
to prevent the diagnostic codes and other data
in its memory from being erased when the
ignition switch is turned off .
There are two types of circuitry for the type
without a stepper motor, depending on the
vehicle model .
To stop lamp switc h
STOP fuse
Battery
* Some models only
®
Engine EC U
BATT
OHP 7
Engine EC U
OHP 7
15