General System Description

Test 1, 2, 3 & 4:

This system combines an electronic fuel and spark advance control system with a cross type intake system to provide a precise air/fuel ratio under all driving conditions. On 1989 models, utilizes a Single Board Engine Controller (SBEC). This system uses a digital pre-programmed computer, to regulate ignition timing, air/fuel ratio, emission control devices, cooling fan, charging system, idle speed and speed control.
Various sensors provide the input necessary for the SBEC to correctly regulate fuel flow at the fuel injectors, Fig. 1. These include manifold absolute pressure, throttle position, oxygen feedback, coolant temperature, charge temperature and vehicle speed sensors. In addition to the sensors, various switches also provide important information. These include transmission neutral safety, brake, speed control and A/C clutch switches. These signals cause the SBEC to change either the fuel flow at the injector, ignition timing or both.
The SBEC tests many of its own input and output circuits. If a problem is detected in a major system, the information is stored in the memory. This information can be displayed by a instrument panel check engine lamp, or by connecting a diagnostic readout tool and reading a numbered display which corresponds to a specific problem.