Toyota Camry 1999 Electrical Troubleshooting Manual page 86

ENGINE CONTROL (5S–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. thus the engine coolant temp. is input in the form of a control signal into
TERMINAL THW of the engine control module.
(2) Intake air temp. signal circuit
The intake air temp. sensor detects the intake air temp., which is input as a control signal into TERMINAL THA of the
engine control module.
(3) Oxygen sensor signal circuit
The oxygen density in the exhaust gases is detected and input as a control signal into TERMINAL OX1 (except
California) and OX2 of the engine control module.
(4) RPM signal circuit
Camshaft position and crankshaft position are detected by the camshaft position sensor and crankshaft position sensor.
Camshaft position is input as a control signal to TERMINAL G+ of the engine control module, and engine RPM is input
into TERMINAL NE+.
(5) Throttle signal circuit
The throttle position sensor detects the throttle valve opening angle, which is input as a control signal into TERMINAL
VTA of the engine control module.
(6) Vehicle speed signal 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) Park/Neutral position SW signal circuit (A/T)
The Park/Neutral position SW detects whether the shift position are in neutral, parking or not, and inputs a control signal
into TERMINAL STA of the engine control module.
(8) A/C SW signal circuit
The A/C amplifier function is built in the engine control module. The A/C SW signal inputs into the TERMINAL A/C SW of
the engine control module.
(9) Battery signal circuit
Voltage is constantly applied to TERMINAL BATT of the engine control module. When the ignition SW is turned on, the
voltage for engine control module start–up power supply is applied to TERMINAL +B of engine control module via EFI
relay.
(10) Intake air volume signal circuit
Intake air volume is detected by the manifold absolute pressure sensor (for manifold pressure) and is input as a control
signal into TERMINAL PIN of the engine control module.
(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 NSW of the engine control module as a control signal.
(12) Engine knock signal circuit
Engine knocking is detected by knock sensor 1 and the signal is input into TERMINAL KNK as a control signal.
(13) Electrical load signal circuit
The signal when systems such as the rear window defogger, headlights, etc. Which cause a high electrical burden are
on is input to TERMINAL ELS as a control signal.
(14) Air fuel ratio signal circuit (California)
The air fuel ratio is detected and input as a control signal into TERMINAL AF+ of the engine control module.