Neutral Start Switch NSW

The Neutral Start Switch input to the ECU is used for ISC control as well as having an influence, although minor, on the fuel delivery program. As it relates to the ISC system, this input is used to determine when to increase idle speed for Engine Load/Speed Change Estimate strategy.

The NSW signal at the ECU will be low (less than 1 volt) as long as the neutral start switch is closed, as it will be with the gear selector in Park or Neutral. This low signal is caused by the voltage drop across R1 which has a relatively high resistance compared to the starter and circuit opening relay coils. When the transmission is shifted into any gear, the neutral start switch opens, causing a halt in current flow through the NSW circuit. This causes an increase in signal voltage at the NSW terminal of the ECU.

In the event this signal malfunctions, the ECU will use the wrong target idle speed for in gear operation and a distinct drop in idle rpm will be noticed as the transmission is shifted from Park or Neutral to any drive gear.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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