Ford F150 Pickup. Instruction - part 1623

pump monitor circuit. 

GENERIC ELECTRONIC MODULE 

Automatic 4-Wheel Drive (A4WD) system is a full time 4-wheel drive system with an electronic shift 4x4 
system that allows the operator to choose between three different 4x4 modes. The operator can switch between 
A4WD, and 4WD high mode at any speed, and 4WD low mode. In A4WD mode, Generic Electronic Module 
(GEM) varies torque split between front and rear driveline by controlling transfer case clutch. Transfer case 
clutch allows for slight speed differences between front and rear driveshaft which normally occurs when 
negotiating a corner on dry pavement. When rear wheels are overpowered, GEM detects this slip condition, and 
duty cycle to transfer case clutch is increased until speed difference between driveshafts is reduced. 

NATURAL GAS VEHICLE MODULE 

Natural Gas Vehicle (NGV) module has 2 functions. The first function is to operate fuel injectors and is referred 
to as Injector Driver Module (IDM). The second function sends a fuel level indicator signal to drive the fuel 
gauge and is called Fuel Indicator Module (FIM). IDM vehicle fuel indicator driver signals are based on PCM 
fuel injector driver signals and are controlled directly by corresponding injector drivers in PCM. IDM must be 
used to provide NG fuel injectors with the required high current necessary for proper operation. The greater 
demand of fuel injector current warrants an increased size of injector driver and increased heat dissipation. 
Given these conditions, PCM would not be suitable for location of these drivers. IDM closely resembles 60-pin 
EEC-IV PCM module in appearance. See NATURAL GAS VEHICLE MODULE LOCATION table. 

IDM injector drivers are capable of controlling amount of current flow to each NG fuel injector. Once fuel 
injector is open, IDM NG fuel injector driver will reduce current flow to a sufficient amount to continue to hold 
fuel injector open in an effort to reduce heat. If IDM driver does not detect required peak current to initially 
open NG fuel injector within a specified amount of time, IDM driver will drop current to fuel injector hold open 
current. The FIM is not part of the powertrain control subsystem. 

NATURAL GAS VEHICLE MODULE LOCATION 

INPUT DEVICES 

NOTE:

F150 5.4L bi-fuel model uses an Alternative Fuel Control Module (AFCM) to 
allow communication between PCM and AFCM. AFCM is incorporated within 
compuvalve on F150 bi-fuel models. For additional information on bi-fuel 
system, see appropriate THEORY & OPERATION - BI-FUEL article.

Application

Location

Crown Victoria 4.6L

Front Of Radiator, On Radiator Support

Econoline 5.4L

Left Rear Of Engine Compartment, Mounted On Fenderwell

Pickup 5.4L

Front Of Radiator, Near Hood Latch

NOTE:

Transmission related PCM inputs 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

  

Vehicles are equipped with different combinations of input devices. Not all devices are used on all models. To 
determine the input device used on a specific model, see WIRING DIAGRAMS . The available input devices 
include the following: 

A/C Cycling Switch 

The A/C Cycling Switch (ACCS) may be wired to either the ACCS or ACPSW PCM input. When the A/C 
cycling switch opens, the PCM will turn off the A/C clutch. 

The ACCS circuit to the PCM provides a voltage signal which indicates when the A/C is requested. When the 
A/C demand switch is turned on, and both the A/C cycling switch and the high pressure contacts of the A/C 
high pressure switch (if equipped and in circuit) are closed, voltage is supplied to the ACCS circuit at the PCM. 
See WIRING DIAGRAMS . 

If the ACCS signal is not received by the PCM, the PCM circuit will not allow the A/C to operate. For 
additional information, see WIDE OPEN THROTTLE A/C CUT-OFF RELAY under PCM OUTPUTS. 

Some applications do not have a dedicated (separate) input to the PCM indicating that A/C is requested. This 
information is received by the PCM through the BUS + and BUS - (SCP) communication. 

Air Conditioning Evaporator Temperature Sensor 

Air Conditioning Evaporative Temperature (ACET) sensor senses evaporator air discharge temperature. ACET 
sensor is a thermistor device in which resistance changes with temperature. Electrical resistance of a thermistor 
decreases as temperature increases, and increases as temperature decreases. PCM sources a low current 5 volts 
on ACET circuit. With SIG RTN also connected to ACET sensor, varying resistance affects voltage drop across 
sensor terminals. As A/C evaporator air temperature changes, varying resistance of ACET sensor changes 
voltage PCM detects. ACET sensor is used to more accurately control A/C clutch cycling, improving 
defrost/demist performance, and reduce A/C clutch cycling. 

Air Conditioning Pressure Sensor 

Air Conditioning Pressure (A/C pressure) sensor is located in high pressure (discharge) side of A/C system. A/C 
pressure sensor provides a voltage signal to PCM that is proportional to A/C pressure. See Fig. 17 . PCM uses 
this information for A/C clutch control, fan control and idle speed control.

NOTE:

Some applications do not have a dedicated (separate) input to PCM indicating 
that A/C is requested. This information is received by PCM through Standard 
Corporate Protocol (SCP) BUS (+) and BUS (-) circuits.

 

2003 Ford Pickup F150 

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

  

Fig. 17: Air Conditioning Pressure Sensor Pressure & Voltage Specification 
Courtesy of FORD MOTOR CO. 

 

2003 Ford Pickup F150 

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

  

A/C High Pressure Switch 

The A/C high pressure switch is used for additional A/C system pressure control. A/C high pressure switch is 
either dual function for 2-speed fan control applications or single function for all other applications. For 
refrigerant containment control, the normally closed high pressure contacts open at a predetermined A/C 
pressure. This will result in A/C turning off, preventing A/C pressure from rising to a level that would open A/C 
high pressure relief valve. For fan control, the normally open medium pressure contacts close at a 
predetermined A/C pressure. This grounds the ACPSW circuit input to Powertrain Control Module (PCM). The 
PCM will then turn on the high speed fan to help reduce A/C pressure. 

Brake Pedal Position Switch 

The Brake Pedal Position (BPP) switch is used by the PCM to disengage the transmission torque converter 
clutch and on some applications as an input to the idle speed control for idle quality and for vehicle speed 
control deactivation. Depending on the vehicle application the BPP switch can be connected to the PCM in the 
following manner:  

z

BPP switch is hard wired to the PCM supplying battery positive voltage (B+) when the vehicle brake is 
applied.  

z

BPP switch is hard wired to a module (ABS, LCM or REM), BPP signal is than broadcasted over the data 
link to be received by the PCM.  

z

BPP switch is hard wired to the anti-lock brake (ABS)- traction control/stability assist module. The 
stability module will interpret the BPP switch input along with other ABS inputs and generate an output 
called the Driver Brake Application (DBA) signal. The DBA signal is than sent to the PCM and to other 
BPP signal users.  

On applications where the BPP switch is hard wired to the PCM and stoplamp circuit, if all stoplamp bulbs are 
burned out (open), high voltage is present at the PCM due to a pull-up resistor in the PCM. This provides fail-
safe operation in the event the circuit to the stoplamp bulbs has failed. 

Brake Pressure Applied/Brake Deactivator Switch 

Brake Pressure Applied (BPA) switch is sometimes called Brake Deactivator switch for vehicle speed control 
deactivation, is a normally closed switch, which supplies battery positive voltage (B+) to PCM when brake 
pedal is not applied. When brake pedal is applied, the normally closed switch will open and power is removed 
from PCM. On some applications the normally closed BPA switch along with the normally open Brake Pedal 
Position (BPP) switch are used for a brake rationality test within PCM. PCM misfire monitor profile learn 
function can be disable if a brake switch failure occurs. If one or both brake pedal inputs to PCM did not change 
states when they were expected to, DTC P1572 may be set by PCM. 

Camshaft Position Sensor 

A 3-pin Hall Effect type Camshaft Position (CMP) sensor or a 2-pin variable reluctance sensor is used. See Fig. 
18 and Fig. 19 . CMP sensor is used to determine camshaft position and to identify when piston No. 1 is on its 
compression stroke. CMP sensor signal is used by PCM for synchronizing the firing of sequential fuel injectors. 
Applications with Coil On Plug (COP) ignition also use CMP signal to select the proper ignition coil to fire. 
The input circuit to PCM is referred to as the CMP input or circuit.

 

2003 Ford Pickup F150 

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