OBD Operation Summary for Fiesta - MotorCraftService.com

Small leak (0.020") detection algorithm:The small leak algorithm is designed to detect a .020" leak in the evaporative purge system as well as a stuck openpurge valve. The small leak (0.020“ diameter) monitor evaluates the data collected from the NVLD II-module during theignition key off/engine off phase. After key off, a leak free evap system will generate a vacuum condition in the fuel tankas the fuel cools down. If the pressure switch in the NVLD II module remains closed for a sufficient time (typically 10minutes), the monitor passes.If a temperature drop of 8°C was observed over at least 2 hours with no significant increase in fuel tank vacuum sincestart of the ignition key off/engine off phase, (i.e. the pressure switch has not closed for the minimum time), a small leakis detected. (P0456)If the diagnostic entry conditions are not met, no diagnostic results are obtained (no call).The overall evap monitor diagnostics are shown in the diagram below. The 0.020: dia leak monitor data is collected bythe NVLD II module during ignition off and evaluated by the ECM during engine-on. The NVLD-II module diagnostics areperformed during ignition on and ignition off.CONTINENTAL REVISED: SEPTEMBER 17, 2010 PAGE 18 OF 111