Ford F150 Pickup. Instruction — part 1643

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

pressure drop across metering orifice required to achieve that flow and outputs corresponding signal to
EGR vacuum regulator solenoid.

3. EGR vacuum regulator solenoid receives a variable duty cycle signal between 0-100 percent. The higher

the duty cycle, the more vacuum the solenoid diverts to EGR valve. For additional EGR vacuum
regulator solenoid information, see EGR VACUUM REGULATOR SOLENOID .

4. The increase in vacuum acting on EGR valve diaphragm overcomes valve spring and begins to lift EGR

valve pintle off its seat, causing exhaust gas to flow into intake manifold.

5. Exhaust gas flowing through EGR valve must first pass through EGR metering orifice (orifice tube).

With one side of orifice exposed to exhaust backpressure and other to intake manifold, a pressure drop is
created across orifice whenever there is EGR flow. When EGR valve closes, there is no longer flow
across metering orifice and pressure on both sides of orifice is the same. PCM constantly targets a desired
pressure drop across metering orifice to achieve desired EGR flow. For additional orifice tube assembly
information, see ORIFICE TUBE ASSEMBLY .

6. DPFE EGR sensor measures actual pressure drop across metering orifice and relays a proportional

voltage signal between 0-5 volts to PCM. See Fig. 74 . PCM uses this feedback signal to correct for any
errors in achieving desired EGR flow. For additional DPFE EGR sensor information, see REMOTE
MOUNTED DIFFERENTIAL PRESSURE FEEDBACK EGR SENSOR or TUBE MOUNTED
DIFFERENTIAL PRESSURE FEEDBACK EGR SENSOR .

Fig. 73: Identifying DPFE EGR System Components & Circuits
Courtesy of FORD MOTOR CO.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

Fig. 74: DPFE EGR Sensor Data & Voltage Output Chart
Courtesy of FORD MOTOR CO.

Differential Pressure Feedback EGR Sensor (Remote Mounted)

Differential Pressure Feedback (DPFE) EGR sensor is a ceramic, capacitive type pressure transducer that
monitors differential pressure across a metering orifice located in orifice tube assembly. DPFE EGR sensor
receives this signal through 2 hoses referred to as downstream pressure hose (REF), and upstream pressure hose
(HI). HI and REF hose connections are marked on aluminum DPFE EGR sensor housing for identification.
Note that HI uses a larger diameter hose. DPFE EGR sensor outputs a voltage proportional to pressure drop
across metering orifice and supplies it to PCM as EGR flow rate feedback. See Fig. 75 .

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline