Toyota 2004 CELICA Electric Troubleshooting Manual page 71

ENGINE CONTROL (1ZZ-FE)
SYSTEM OUTLINE
This system utilizes an engine control module and maintains overall control of the engine, transmission and so on. An outline
of the engine control is explained here.
1. INPUT SIGNALS
(1) Engine coolant temp. signal circuit
The engine coolant temp. sensor detects the engine coolant temp. and has a built-in thermistor with a resistance which
varies according to the engine coolant temp. The engine coolant temp. is input into TERMINAL THW of the engine
control module as a control signal.
(2) Intake air temp. signal circuit
The intake air temp. sensor is installed in the mass air flow meter and detects the intake air temp., which is input as a
control signal to TERMINAL THA of the engine control module.
(3) Oxygen sensor signal circuit
The oxygen density in the exhaust emission is detected and is input as a control signal from the heated oxygen sensors
(Bank 1 sensor 1, bank 1 sensor 2) to TERMINALS OX1A, OX1B of the engine control module.
To stabilize detection performance by the heated oxygen sensors, the heated oxygen sensors are warmed. This heater
is also controlled by the engine control module (HT1A, HT1B).
(4) RPM signal circuit
Camshaft position is detected by the camshaft position sensor and its signal is input to TERMINAL G2 of the engine
control module as a control signal. Also, the engine RPM is detected by the crankshaft position sensor installed in the
cylinder block and the signal is input into TERMINAL NE+ of the engine control module as a control signal.
(5) Throttle signal circuit
The throttle position sensor detects the throttle valve opening angle as a control signal, which is input into TERMINAL
VTA of the engine control module.
(6) Vehicle speed circuit
The vehicle speed sensor, installed inside the transmission, detects the vehicle speed and inputs a control signal into
TERMINAL SPD of the engine control module.
(7) A/C SW signal circuit
The operating voltage of the A/C magnetic clutch is detected and the signal is input into TERMINAL ACMG of the engine
control module as a control signal.
(8) Battery signal circuit
Voltage is constantly applied to TERMINAL BATT of the engine control module. With the ignition SW turned on, Voltage
for engine control module start-up power supply is applied to TERMINAL +B of the engine control module via the EFI
relay.
(9) Intake air volume signal circuit
Intake air volume is detected by the mass air flow meter and the signal is input to TERMINAL VG of the engine control
module as a control signal.
(10) Stop light SW signal circuit
The stop light SW is used to detect whether or not the vehicle is braking and the signal is input into TERMINAL STP of
the engine control module as a control signal.
(11) Starter signal circuit
To confirm whether the engine is cranking, the voltage applied to the starter motor during cranking is detected and the
signal is input into TERMINAL STA of the engine control module as a control signal.
(12) Engine knock signal circuit
Engine knocking is detected by knock sensor and the signal is input into TERMINAL KNK1 as a control signal.
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2004 CELICA (EWD538U)