Engine Sensors

The computer needs information to determine engine operating conditions and requirements. The air flowmeter, fuel flowmeter, fuel pressure switch, fuel temperature switch and throttle sensors are described in air and fuel sections. Other sensors include oxygen sensor, engine coolant temperature (used to compute warm-up enrichment), and a back-up closed throttle switch. This switch is actually a brake switch in parallel with the idle stop switch. It ensures that the engine idle is controlled when the brake is depressed.

The computer also calculates engine speed from distributor signals, engine load by dividing airflow and speed, and A/C operation by compressor clutch voltage. These inputs are used to modify spark timing and fuel injection. In addition, emission systems like canister purge and air injection are controlled.