2002 MY OBD-II System Operation Summary - MotorCraftService.com

Fuel System MonitorAs fuel system components age or otherwise change over the life of the vehicle, the adaptive fuel strategy learnsdeviations from stoichiometry while running in closed loop fuel. These learned corrections are stored in KeepAlive Memory as long term fuel trim corrections. They may be stored into an 8x10 rpm/load table or they may bestored as a function of air mass. As components continue to change beyond normal limits or if a malfunctionoccurs, the long term fuel trim values will reach a calibratable rich or lean limit where the adaptive fuel strategy isno longer allowed to compensate for additional fuel system changes. Long term fuel trim corrections at their limits,in conjunction with a calibratable deviation in short term fuel trim, indicate a rich or lean fuel system malfunction.Fuel Monitor Operation:DTCsMonitor executionMonitor SequenceSensors OKMonitoring DurationP0171 Bank 1 Lean, P0174 Bank 2 LeanP0172 Bank 1 Rich, P0175 Bank 2 Richcontinuous while in closed loop fuelnoneFuel Rail Pressure (if available)2 seconds to register malfunctionTypical fuel monitor entry conditions:Entry condition Minimum MaximumRPM Range idle 4,000 rpmAir Mass Range0.75 lb/minPurge Dutycycle 0% 0%Typical fuel monitor malfunction thresholds:Long Term Fuel Trim correction cell currently being utilized in conjunction with Short Term Fuel Trim:Lean malfunction: LTFT > 25%, STFT > 5%Rich malfunction: LTFT < 25%, STFT < 10%FORD MOTOR COMPANY REVISION DATE: OCTOBER 02, 2001 PAGE 23 OF 66