Ford F150 Pickup. Instruction - part 1627

Fig. 24: Identifying Thermal Manifold Absolute Pressure Sensor 
Courtesy of FORD MOTOR CO. 

Throttle Position Sensor 

Throttle Position (TP) sensor is a rotary potentiometer sensor that provides a signal to PCM that is linearly 
proportional to throttle plate/shaft position. TP sensor housing has a 3-blade electrical connector that may be 
gold plated. The gold plating increases corrosion resistance on terminals and increases connector durability. TP 

 

2003 Ford Pickup F150 

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

  

sensor is mounted on throttle body and has 4 operating conditions: closed throttle (idle or deceleration), part 
throttle (cruise or moderate acceleration), wide open throttle (includes maximum acceleration or de-choke on 
crank), and throttle angle rate. TP sensor signal affects air/fuel ratio, injector timing, idle speed, EGR flow and 
ignition timing. 

Transmission Control Switch 

Transmission Control Switch (TCS) may also be referred to as overdrive (O/D) cancel switch. The TCS signals 
the PCM with keypower whenever the TCS is pressed. TCS position is controlled by vehicle operator. If 
overdrive is disengaged, O/D OFF indicator located on instrument panel, or Transmission Control Indicator 
Light (TCIL) located on shift lever, will illuminate. 

Vehicle Speed Sensor 

Vehicle Speed Sensor (VSS) is a variable reluctance or Hall Effect type sensor that generates a waveform with a 
frequency that is proportional to vehicle speed. When vehicle is moving slowly, sensor produces a low 
frequency signal. As vehicle speed increases, sensor produces a higher frequency signal. PCM uses this signal 
to control fuel injection, ignition timing and transaxle/transmission shift and Torque Converter Clutch (TCC) 
scheduling. 

4x4 Mode Switch 

Generic Electronic Module (GEM) provides PCM with an indication of 4x4L. This input is used to adjust 
transmission shift scheduling. A 5-volt module pull-up indicates 4x4H or 2WD. See Fig. 25 . 

 

2003 Ford Pickup F150 

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

  

Fig. 25: Identifying 4x4 Mode Switch 
Courtesy of FORD MOTOR CO. 

 

2003 Ford Pickup F150 

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

  

OUTPUT DEVICES 

Vehicles are equipped with different combinations of computer controlled components. Not all components 
listed are used on every vehicle. For theory and operation on each output component, refer to system indicated 
after component. 

Canister Vent Solenoid 

See FUEL EVAPORATIVE SYSTEM under EVAPORATIVE EMISSION SYSTEMS. 

Coil Pack 

A coil in a coil pack is turned on (coil charging) by PCM, and is turned off when 2 spark plugs are fired 
simultaneously. Spark plugs are paired so that one spark plug fires on the compression stroke and other spark 
plug fires on exhaust stroke. Next time coil is fired, order is reversed and next pair of spark plugs fire according 
to engine firing order. 

Coil On Plug 

Coil On Plug (COP) ignition operates similar to a standard coil pack ignition except each spark plug has one 
coil per spark plug. See Fig. 26 . COP has 3 different modes of operation:  

z

Engine Cranking 
 
During engine cranking, PCM will fire 2 spark plugs simultaneously. One spark plug will fire on 
compression stroke and the other spark plug fires on exhaust stroke. Both spark plugs will fire until 
camshaft position is identified by a successful camshaft sensor signal. 

z

Engine Running 
 
Once camshaft position is identified and engine is running, only spark plug with cylinder under 
compression will be fired. 

z

CMP Failure Mode Effects Management (CMP FMEM) 
 
During CMP FMEM, COP ignition operates similar to engine cranking mode. This allows engine to 
operate without requiring PCM to know if cylinder is on compression or exhaust stroke. 

NOTE:

Transmission related PCM outputs are not listed here. For a complete listing of 
transmission related PCM inputs, see appropriate DIAGNOSIS article in 
AUTOMATIC TRANSMISSIONS.

 

2003 Ford Pickup F150 

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