Coolant Temperature Sensors

There are 3 components which supply coolant temperature information to the MCU. They are the coolant temperature switch, coolant temperature sensor and the thermo timer. All 3 devices are located in the water jacket of the engine block.

These devices supply coolant temperature information to the MCU in the form of electrical signals. The MCU interprets these signals as cold or normal operating temperatures. When the MCU has determined optimum ignition timing (based on input from various sources) information supplied by the reference point pickup sensor is used to signal ignition firing.

During cold operating conditions, the air/fuel mixture is enriched by the cold start valve. This valve is located in the intake manifold, downstream from the butterfly valve. It supplies additional fuel to the inlet charge when signaled by the MCU. Extra rich conditions are maintained until normal operating temperature is attained.