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

After the vehicle has warmed up and normal EGR rates are being commanded by the PCM, the low flow check isperformed. Since the EGR system is a closed loop system, the EGR system will deliver the requested EGR flow aslong as it has the capacity to do so. If the EVR duty cycle is very high (greater than 80% duty cycle), the differentialpressure indicated by the DPFE sensor is evaluated to determine the amount of EGR system restriction. If thedifferential pressure is below a calibratable threshold, a low flow malfunction in indicated (P0401).EGR Flow Check Operation:DTCsMonitor executionMonitor SequenceSensors OKMonitoring DurationP0401once per driving cycleDone after P1405 and P1406 testsCPS, ECT, IAT, MAF, TP70 seconds to register a malfunctionTypical EGR flow check entry conditions:Entry Condition Minimum MaximumEVR Dutycycle 80% 100%Engine RPM2500 rpmMass Air Flow Rate of Change6% program loopInferred manifold vacuum 6 in Hg 10 in HgTypical EGR flow check malfunction thresholds:DPFE sensor voltage: < 6 in H 2 OJ1979 Mode $06 DataTest ID Comp ID Description Units$4A $30 Delta pressure for flow test and thresholdTID 4A replaced by 49 in new 2000 MY softwarein. H 2 0$49 $30 Delta pressure for flow test and threshold in. H 2 0$4B $30 EVR dutycycle for flow test and threshold percentConversion for Test ID $4A: If value is > 32,767, the value is negative. Take value, subtract 65,536, and thenmultiply result by 0.0078 to get inches of H 2 0. If value is