Fuel Injection System - TBI: Description
The throttle body fuel injection system is controlled by a pre-programmed digital computer (logic module). The logic module controls ignition timing, emission control devices, idle speed and air/fuel ratio. The logic module converts input signals from sensors and switches into control signals.
The logic module tests many of its own input and output circuits. If a fault is found in a major system, this information is stored in the logic module. Information on this fault can be displayed by the use of the instrument panel power loss light or by connecting a diagnostic read out and reading a numbered display code which directly relates to a general fault.
Input sensors used by logic module are manifold absolute pressure sensor (MAP) sensor, throttle position sensor (TPS), oxygen sensor, coolant temperature sensor, throttle body temperature sensor and vehicle distance sensor. Switches used include idle switch, neutral safety switch, A/C clutch switch and brake light switch.
Control (output) signals from logic module are sent to power module. Power module then sends electrical signal to appropriate component in order to alter mixture and/or ignition timing. Amount of fuel metered through injector is controlling factor in air/fuel ratio.