The STA signal is used by the ECU to allow additional air to enter the intake manifold while cranking the engine. Additionally, it is used to determine when to enrich injection for starting and when to operate the Fuel Pressure-Up (FPU) system. In the event that the STA signal malfunctions, the engine may be difficult to start.
The STA signal at the ECU will be low at all times except while the engine is cranking. While cranking, the STA signal goes high (cranking voltage) as current flows through the closed ignition switch and neutral start switch contacts.
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