Control System; Diagnosis System; Fail-Safe System - Toyota Camry 1999 Electrical Troubleshooting Manual

ENGINE CONTROL (1MZ–FE)

2. CONTROL SYSTEM

∗ SFI system
The SFI system monitors the engine condition through the signals, which are input from each sensor (Input signals (1) to
(12) ). The best fuel injection volume is decided based on this data and the program memorized by the engine control
module, and the control signal is output to TERMINALS #10, #20, #30, #40, #50 and #60 of the engine control module
to operate the injector (Inject the fuel). The SFI system produces control of fuel injection operation by the engine control
module in response to the driving conditions.
∗ ESA system
The ESA system monitors the engine condition through the signals, which are input to the engine control module from
each sensor (Input signals from 1, 3, 4, 12). The best ignition timing is decided according to this data and the memorized
data in the engine control module and the control signal is output to TERMINALS IGT1, IGT2 and IGT3. This signal
controls the igniter to provide the best ignition timing for the driving conditions.
∗ Heated oxygen sensor heater control system
The heated oxygen sensor heater control system turns the heater on when the intake air volume is low (Temp. of
exhaust emissions is low), and warms up the heated oxygen sensor to improve detection performance of the sensor.
The engine control module evaluates the signals from each sensor (Input signals from 1, 4, 9, 10), current is output to
TERMINALS HTL, HTR and HTS, controlling the heater.
∗ Idle air control system
The idle air control system (Rotary solenoid type) increases the RPM and provides idle stability for fast idle–up when the
engine is cold, and when the idle speed has dropped due to electrical load and so on, the engine control module
evaluates the signals from each sensor (Input signals from 1, 4, 5, 8, 9), current is output to TERMINALS RSO and RSC
to control idle air control valve.
∗ EGR control system
The EGR control system detects the signal from each sensor (Input signals from 1, 4, 9, 10), and outputs current to
TERMINAL EGR to control the VSV (EGR).
The EGR valve position sensor is mounted on the EGR valve. this sensor converts the EGR valve opening height into a
voltage and sends it to the engine control module as the EGR valve position signal.
∗ ACIS
ACIS includes a valve in the bulkhead separating the surge tank into two parts. This valve is opened and closed in
accordance with the driving conditions to control the intake manifold length in two stages for increased engine output in
all ranges from low to high speeds.
The engine control module judges the engine speed by the signals ( (4), (5) ) from each sensor and outputs signals to
the TERMINAL ACIS to control the VSV (Intake air control).

3. DIAGNOSIS SYSTEM

With the diagnosis system, when there is a malfunction in the engine control module signal system, the malfunctioning
system is recorded in the memory.
4. FAIL–SAFE SYSTEM
When a malfunction occurs in any systems, if there is a possibility of engine trouble being caused by continued control
based on the signals from that system, the fail–safe system either controls the system by using data (Standard values)
recorded in the engine control module memory or else stops the engine.