OBD Operation Summary for 6.7L Diesel - MotorCraftService.com

I/M Readiness CodeThe readiness function is implemented based on the J1979 format. Clearing codes using a scan tool results inthe various I/M readiness bits being set to a “not-ready” condition. As each non-continuous monitor completes afull diagnostic check, the I/M readiness bit associated with that monitor is set to a “ready” condition. This may takeone or two driving cycles based on whether malfunctions are detected or not.Power Take Off ModeWhile PTO mode is engaged, the I/M readiness bits are set to a “not-ready” condition. When PTO mode isdisengaged, the I/M readiness bits are restored to their previous states prior to PTO engagement. During PTOmode, only CCM circuit checks continue to be performed.Serial Data Link MIL IlluminationThe OBD-II diagnostic communication messages utilize an industry standard 500 kbps CAN communication link.The instrument cluster on some vehicles uses the same CAN data link to receive and display various types ofinformation from the PCM. For example, the engine coolant temperature information displayed on the instrumentcluster comes from the same ECT sensor used by the PCM for all its internal calculations.These same vehicles use the CAN data link to illuminate the MIL rather than a circuit, hard-wired to the PCM.The PCM periodically sends the instrument cluster a message that tells it to turn on the MIL, turn off the MIL orblink the MIL. If the instrument cluster fails to receive a message within a 5-second timeout period, the instrumentcluster itself illuminates the MIL. If communication is restored, the instrument cluster turns off the MIL after 5seconds. Due to its limited capabilities, the instrument cluster does not generate or store Diagnostic TroubleCodes.FORD MOTOR COMPANY REVISION DATE: FEBRUARY 9, 2012 09.01.00.02-PAGE 156 OF 157