OBD Operation Summary for 6.7L Diesel - MotorCraftService.com

General Description 6.7L Diesel EngineThe 6.7L is a V8 engine designed to meet customer expectations of high horsepower and torque with exceptionalfuel economy and low NVH. It must do this while meeting the tough emissions standards set by the EPA andCARB.Some of the technologies employed to meet these diverse criteria include a Variable Geometry Turbocharger(VGT), common rail fuel injection system, electronically controlled, cooled EGR, a diesel oxidation catalyst (DOC) ,Selective Catalytic Reduction catalyst (SCR), Diesel Exhaust Fluid (DEF) injection system, and a diesel particulatefilter (DPF).The system schematic on the next page shows the path of the air as it is compressed by the turbocharger, cooledby the air-to-coolant intercooler, and mixed with the cooled EGR gases. The state of this compressed and heatedair is sensed by the manifold absolute pressure (MAP) sensor just before it enters the cylinders and the twotemperature sensors that represent Charge Air Cooler Outlet temperature (CACT1) and EGR Cooler outlettemperature (EGRCOT). The exhaust gas pressure is measured by the exhaust backpressure (EP) sensor beforeit exits through the turbocharger. The exhaust after treatment system consists of a DOC, a SCR, a DPF and amuffler.An electronic, proportional valve controls EGR rates with an integral position sensor (EGRP). Flows aredetermined by valve position and the amount that backpressure exceeds boost pressure. An EGR throttle(EGRTP) is used for regeneration control as well as to optimize the boost pressure vs. backpressure levels.Fuel injection pressure is measured by the high-pressure fuel rail sensor (FRP). Injection pressure is controlled bythe high pressure pump and two regulating valves, a Pressure Control Valve (PCV), and a Fuel Metering Unit(MeUn), formerly known as Volume Control Valve (VCV).Engine speed (N) and crankshaft position are determined by the crankshaft position sensor (CKP) which senses a60 minus 2 tooth target wheel. Camshaft position is determined by the camshaft position sensor (CMP), whichsenses the profile of a multiple lobed camshaft.Atmospheric pressure is determined by the Barometric Pressure sensor (BARO) mounted internally in the EngineControl Module (ECM).During engine operation, the ECM calculates engine speed from the crankshaft position sensor. The ECMcontrols engine operation by controlling the piezo injector opening and closing times as well as the pressure atwhich the fuel is injected, thereby controlling fuel quantity and timing. Simultaneously, airflow is modulated bycontrolling the turbocharger vane position.Fuel quantity is controlled by injector “on time” (pulse width) and the fuel rail pressure. Desired engine speed isdetermined from the position of the accelerator pedal.FORD MOTOR COMPANY REVISION DATE: FEBRUARY 9, 2012 09.01.00.02-PAGE 8 OF 157