Secondary AIR by-pass solenoid is used by PCM to control vacuum to secondary AIR diverter valve. AIR by-
pass solenoid is a normally closed solenoid. AIR by-pass solenoid also has a filtered vent feature to permit
vacuum release. See Fig. 72 .
AIR Diverter Valve
The secondary air injection diverter (AIR diverter) valve is used with Electric Air Pump (EAP) to provide
on/off control of air to exhaust manifold and catalytic converter. See Fig. 72 . When EAP is on and vacuum is
supplied to AIR diverter valve, air passes integral check valve disk. When EAP is off, and vacuum is removed
from AIR diverter valve, integral check valve disk is held on the seat and stops air from being drawn into
exhaust system and prevents backflow of exhaust into secondary air injection system.
Electric AIR Pump
Electric AIR Pump (EAP) provides pressurized air to secondary air injection system. EAP functions
independently of RPM and is controlled by PCM. EAP is used for short periods of time. Delivery of air is
dependent on amount of system backpressure and system voltage. Inlet system of EAP incorporates a non-
serviceable filter and splash cap which helps to guard against dirt and water. See Fig. 72 .
EGR SYSTEMS
DESCRIPTION
Exhaust Gas Recirculation (EGR) system controls oxides of nitrogen (NOx) emissions. Small amounts of
exhaust gases are recirculated back into combustion chamber to be reburned with air/fuel charge. There are 2
different types of EGR systems that may be used:
z
DIFFERENTIAL PRESSURE FEEDBACK EGR SYSTEM
z
ELECTRIC MOTOR EGR SYSTEM
DIFFERENTIAL PRESSURE FEEDBACK EGR SYSTEM
Differential Pressure Feedback (DPFE) EGR system consists of a DPFE EGR sensor, EGR vacuum regulator
solenoid, EGR valve, orifice tube assembly and Powertrain Control Module (PCM). The following list of
components and their specific operation corresponds to numbers in illustration. See Fig. 73 .
1. DPFE EGR system receives signals from Engine Coolant Temperature (ECT) sensor, Intake Air
Temperature (IAT) sensor, Throttle Position (TP) sensor, Mass Airflow (MAF) sensor and Crankshaft
Position (CKP) sensor to provide information on engine operating conditions to PCM. Engine must be
warm, stable and running at a moderate load and engine speed (RPM) before EGR system is activated.
PCM deactivates EGR during idle, extended Wide Open Throttle (WOT), or whenever a failure is
detected in an EGR component or EGR required input.
2. PCM calculates desired amount of EGR flow for a given engine condition. It then determines desired
NOTE:
The self-diagnostic system monitors EGR system performance and sets a
Diagnostic Trouble Code (DTC) if self-test requirements are not obtained.
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline