Ford F150 Pickup. Instruction - part 1642

Courtesy of FORD MOTOR CO. 

Fig. 69: Identifying EVAP System Components (LS & Thunderbird) 
Courtesy of FORD MOTOR CO. 

POSITIVE CRANKCASE VENTILATION 

The Positive Crankcase Ventilation (PCV) system cycles crankcase gases back through the engine where they 
are burned. The PCV valve regulates the amount of ventilating air and blow-by gas to the intake manifold and 
prevents backfire from traveling into the crankcase. The PCV valve is designed with a quarter-turn cam-lock 
thread at one end to prevent accidental disconnection from the valve cover. 

SECONDARY AIR INJECTION SYSTEM 

DESCRIPTION 

The Secondary Air Injection (AIR) system controls emissions during first 20-120 seconds of engine operation 
by forcing air downstream into exhaust manifolds to oxidize hydrocarbons and carbon monoxide created by 
running rich at start up. 

ELECTRIC SECONDARY AIR INJECTION SYSTEM 

CAUTION: DO NOT remove PCV system from engine. Removal of PCV system will 

adversely affect fuel economy and engine ventilation and result in shorter 
engine life.

 

2003 Ford Pickup F150 

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

  

Electric Secondary Air Injection (AIR) system consists of an Electric AIR Pump (EAP), single or dual 
combination check air injection diverter (AIR diverter) valve(s), an AIR by-pass solenoid, a solid state relay, 
PCM, wiring and vacuum hoses. The following list of components and their specific operation corresponds to 
numbers in illustration. See Fig. 70 .  

1. PCM requires Engine Coolant Temperature (ECT), Intake Air Temperature (IAT) and Crankshaft 

Position (CKP) inputs to initiate secondary air injection function.  

2. When engine is started, strategy will determine when to enable Electric Air Pump (EAP). After a 5-10 

second delay, PCM signals solid state relay and AIR by-pass solenoid to begin system operation. Once 
catalyst is lit-off, PCM then signals solid state relay to stop EAP operation and to close AIR by-pass 
solenoid from supplying vacuum to AIR diverter valve(s). For additional AIR by-pass solenoid or AIR 
diverter valve information, see AIR BY-PASS SOLENOID or AIR DIVERTER VALVE .  

3. Solid state relay provides start-up signal and will switch high current required to operate EAP. Input 

control to solid state relay comes from PCM. See Fig. 71 .  

4. AIR by-pass solenoid applies a vacuum to AIR diverter valve(s) causing it to open and to allow air to 

flow into exhaust manifolds.  

5. Vacuum check valve controls vacuum bleed-off to solenoid.  

6. Function of splash cap, if equipped, is to provide EAP with a source of dry air.  

7. EAP delivers required amount of air to control emissions during engine operation. Air is forced into 

exhaust manifolds to oxidize hydrocarbons and carbon monoxide created by running rich at start up. For 
additional EAP information, see ELECTRIC AIR PUMP .  

Fig. 70: Identifying Electric Secondary Air Injection System Components & Circuits 
Courtesy of FORD MOTOR CO. 

 

2003 Ford Pickup F150 

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

  

Fig. 71: Identifying Solid State Relay 
Courtesy of FORD MOTOR CO. 

 

2003 Ford Pickup F150 

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

  

Fig. 72: Identifying Secondary AIR Injection Components 
Courtesy of FORD MOTOR CO. 

AIR By-Pass Solenoid 

 

2003 Ford Pickup F150 

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