A thermistor built into the engine coolant temperature sensor changes the resistance value according to the engine coolant temperature. The structure of the sensor and connection to the ECM is the same as in the intake air temp. circuit malfunction shown on page DI-26 . If the ECM detects the DTC P0115, it operates the fail-safe function in which the engine coolant temp. is assumed to be 80°C (176°F).
HINT: After confirming DTC P0115 use the OBD II scan tool or TOYOTA hand-held tester to confirm the engine coolant temperature from ”CURRENT DATA”.
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By a built-in sensor unit, the manifold absolute pressure sensor detects the intake manifold pressure as a voltage. The ECM then determines the basic injection duration and basic injection advance angle based on this voltage. Since the manifold absolute pressure sensor does not use the atmospheric pressure as a criterion, but senses the absolute pressure inside the intake manifold (the pressure in proportion to the present absolute vacuum 0), it is not influenced by fluctuations in the atmospheric pressure due to high altitude and other factors. This permits it to control the air-fuel ratio at the proper lever under all conditions.
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This article contains underhood views or schematics of vacuum hose routing. Use these vacuum diagrams during the visual inspection in F – BASIC TESTING. This will assist in identifying improperly routed vacuum hoses which cause driveability and/or computer-indicated malfunctions.
1991 ENGINE PERFORMANCE Vacuum Diagrams Camry, Celica, Corolla, Cressida, Land Cruiser, MR2, Pickup, Previa, Supra, Tercel, 4Runner.
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