Neutral Gear Switch is installed in M/T vehicle and senses driver’s intension to shift gear(driver’s intension to drive). ECM recognizes engaged gear based on vehicle speed sensor signal and engine RPM in M/T vehicle. And Black Smoke limiting fuel quantity value varies according to engaged gear.(As higher gear shift is engaged, maximum possible fuel injection quantity increases to raise power generation.) The recognition of engaged gear is available when vehicle speed reachs to 2Km/h - the minimum speed for ECM to detect. When vehicle starts to move after standing for a while and vehicle speed does not reach to 2Km/h, fuel quantity mapping value at neutral gear is adopted to vehicle. Moreover, this phenomenon is more serious when vehicle requires high power generation such as the situation when vehicle is on the slope. To cope with this problem, neutral gear switch which senses driver’s intension of starting to move is applied. And fuel injection quantity mapping value suitable for 1st gear is adopted immediately.

P0820 is set when 1)gear is engaged at engine ON, but clutch signal is not detected for more than 3 sec. or 2)only neutral signal is detected at above 80Km/h. for more than 12 sec.. This code is due to open, short to battery or ground in neutral gear switch circuit.