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

HO2S Heaters, front and rearThe HO2S heaters are monitored for proper voltage and current. A HO2S heater voltage fault is determined byturning the heater on and off and looking for corresponding voltage change in the heater output driver circuit in thePCM.A separate current-monitoring circuit monitors heater current once per driving cycle. The heater current is actuallysampled three times. If the current value for two of the three samples falls below a calibratable threshold, theheater is assumed to be degraded or malfunctioning. (Multiple samples are taken for protection against noise onthe heater current circuit.)HO2S Heater Monitor Operation:DTCsMonitor executionMonitor SequenceSensors OKMonitoring DurationBank 1 - P0135 Front, P0141 RearBank 2 - P0155 Front, P0161 Rearonce per driving cycle for heater current, continuous for voltage monitoringheater voltage check is done prior to heater current check< 5 secondsTypical HO2S heater monitor entry conditions:Entry condition Minimum MaximumInferred exhaust temperature range 250 o F 1400 o FHO2S heater-on time120 secondsTypical HO2S heater check malfunction thresholds:Smart driver status indicated malfunctionHeater current outside limits: < 0.220 amps or > 3 amps, (NTK)< 0.400 amps or > 3 amps, (Bosch)< 0.465 amps or > 3 amps, (NTK Fast Light Off)< 0.230 amps or > 3 amps, (Bosch Fast Light Off)FORD MOTOR COMPANY REVISION DATE: OCTOBER 02, 2001 PAGE 27 OF 66