Ford F150 Pickup. Instruction - part 1621

Fig. 16: Identifying 150-Pin PCM Connector Terminals (All Others) 
Courtesy of FORD MOTOR CO. 

Hardware Limited Operation Strategy 

HLOS is a system of alternate circuitry that provides minimal engine operation if the PCM or EEPROM fails. 
During HLOS, all self-test function will stop and system will be controlled by electronic hardware.  

HLOS Allowable Output Functions: 

z

Spark Output Controlled Directly By CKP Signal  

z

Fixed Fuel Pulse Width Synchronized With CKP Signal  

z

Fuel Pump Relay Energized  

 

2003 Ford Pickup F150 

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

  

z

Idle Speed Control Output Signal Functional  

HLOS Disabled Outputs To Default State: 

z

EGR Solenoids  

z

No Torque Converter Clutch Lock-Up  

Integrated Electronic Ignition System 

Integrated Electronic Ignition (EI) System consists of a Crankshaft Position (CKP) sensor, coil pack(s), 
connecting wiring, and PCM. Coil On Plug (COP) Integrated EI System uses a separate coil for each spark plug 
and each coil is mounted directly onto plug. COP Integrated EI System eliminates the need for spark plug wires 
but does require input from Camshaft Position (CMP) sensor. For additional EI system information, see 
INTEGRATED ELECTRONIC IGNITION SYSTEM under IGNITION SYSTEMS. 

Keep Alive Random Access Memory 

Keep Alive Random Access Memory (KAM) stores memory of vehicle operating conditions and then uses this 
information for adaptive learning. KAM remains powered with ignition off so that input and output information 
is not lost. 

POWER & GROUND SIGNALS 

Vehicle Buffered Power 

Vehicle Buffered Power (VBPWR) is a PCM supplied power source that supplies regulated voltage (10-14 
volts) to Vistronic Drive Fan (VDF) Fan Speed Sensor (FANSS) under normal operating conditions. It regulates 
to VPWR minus 1.5 volts, and voltage output is limited to protect sensor. For additional VDF clutch 
information, see VISTRONIC DRIVE FAN under OUTPUT SIGNALS. 

Vehicle Power 

When ignition switch is turned to START or RUN position, battery positive voltage (B+) is applied to coil of 
PCM power relay. Since other end of coil is wired to ground, this energizes coil and closes contacts of PCM 
power relay. Vehicle power (VPWR) is now sent to PCM and various OBD-II systems. 

Vehicle Reference Voltage 

Vehicle Reference Voltage (VREF) is a positive voltage (about 5 volts) that is output by PCM. This is a 
consistent voltage that is used by 3-wire sensors. 

Mass Air Flow Return 

Mass Air Flow Return (MAF RTN) is a dedicated analog signal return from Mass Air Flow (MAF) sensor. It 
serves as a ground offset for analog voltage differential input by MAF sensor to PCM. 

Signal Return 

 

2003 Ford Pickup F150 

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

  

Signal Return (SIG RTN) is a dedicated ground circuit used by most OBD-II sensors and some other inputs.

Power Ground 

Power Ground (PWR GND) is an electric current path return for VPWR voltage circuit. The purpose of PWR 
GND is to maintain sufficient voltage at PCM. 

Gold Plated Terminals 

Some engine control hardware has gold plated terminals on connectors and mating harness connectors to 
improve electrical stability for low current draw circuits and to enhance corrosion resistance. OBD-II 
components equipped with gold terminals will vary by vehicle application. 

POWERTRAIN CONTROL MODULE SOFTWARE 

Engine RPM/Vehicle Speed Limiter 

PCM will disable some or all fuel injectors whenever an engine RPM or vehicle overspeed condition is 
detected. This prevents damage to the powertrain. Excessive wheel slippage caused by sand, gravel, rain, mud, 
snow, ice, etc. or excessive and sudden increase in RPM while in NEUTRAL or while driving may cause 
engine RPM/vehicle speed limiter to be enabled. When engine RPM/vehicle speed limiter has been enabled, 
vehicle will exhibit a rough running engine condition, and PCM will store DTC P1270. After driver reduces 
excessive speed, engine will return to normal operating mode. No repairs are required. Technician should clear 
DTC from PCM and inform customer of the reason for DTC. Excessive wheel slippage may be caused by sand, 
gravel, rain, mud, snow, ice, etc. or excessive and sudden increase in RPM while in Neutral or while driving. 

Fail-Safe Cooling Strategy 

Fail-safe cooling strategy is activated by PCM only in the event that an overheating condition has been 
detected. This strategy provides engine temperature control when cylinder head temperature exceeds certain 
limits. Cylinder head temperature is measured by Cylinder Head Temperature (CHT) sensor. For additional 
CHT sensor information, see CYLINDER HEAD TEMPERATURE SENSOR under INPUT DEVICES. 

A cooling system failure such as low coolant or coolant loss could cause an overheating condition. As a result, 
damage to major engine components could occur. Along with a CHT sensor, fail-safe cooling strategy is used to 
prevent damage by allowing air cooling of engine. This strategy allows the vehicle to be driven safely for a 
short time with some loss of performance when an overheating condition exists. Engine temperature is 
controlled by varying and alternating the number of disabled fuel injectors. This allows all cylinders to cool. 
When fuel injectors are disabled, their respective cylinders work as air pumps, and this air is used to cool the 
cylinders. The more fuel injectors that are disabled, the cooler the engine runs, but the engine has less power. 

NOTE:

Damaged gold terminals should only be replaced with NEW gold terminals.

NOTE:

Not all vehicles equipped with a CHT sensor will have fail-safe cooling strategy.

NOTE:

A Wide Open Throttle (WOT) delay is incorporated if CHT temperature is 

 

2003 Ford Pickup F150 

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

  

Before injectors are disabled, fail-safe cooling strategy alerts customer to a cooling system problem by moving 
instrument cluster temperature gauge to HOT zone and a PCM DTC P1285 is set. Depending on the vehicle, 
other indicators, such as an audible chime or warning lamp, can be used to alert customer of fail-safe cooling. If 
overheating continues, fail-safe cooling strategy begins to disable fuel injectors, a DTC P1299 is stored in PCM 
memory and a Malfunction Indicator Light (MIL), either CHECK ENGINE or SERVICE ENGINE SOON will 
illuminate. If overheating condition continues and a critical temperature is reached, all fuel injectors are turned 
off and engine is disabled. 

Failure Mode Effects Management 

Failure Mode Effects Management (FMEM) is an alternate system strategy in PCM designed to maintain engine 
operation if one or more sensor inputs fail. When a sensor input is perceived to be out-of-limits by PCM, an 
alternative strategy is initiated. PCM substitutes a fixed value and continues to monitor incorrect sensor input. If 
suspect sensor operates within limits, PCM returns to normal engine operational strategy. All FMEM sensors 
display a sequence error message on scan tool. Message may or may not be followed by Key On Engine Off 
(KOEO) or Continuous Memory DTCs when attempting Key On Engine Running (KOER) self-test mode. 

Flash Electrically Erasable Programmable Read Only Memory 

Flash Electrically Erasable Programmable Read Only Memory (EEPROM) is an Integrated Circuit (IC) within 
PCM. This IC contains software code required by PCM to control powertrain. EEPROM can be electrically 
erased and then reprogrammed without removing PCM from vehicle. If a software change is required to PCM, 
PCM can be reprogrammed through Data Link Connector (DLC) using scan tool. 

Fuel Trim 

Short Term Fuel Trim. If the oxygen sensors are warmed up and the PCM determines that the engine can 
operate near stoichiometric air/fuel ratio (14.7 to 1 for gasoline), the PCM goes into closed loop fuel control 
mode. Since an oxygen sensor can only indicate rich or lean, the fuel control strategy must constantly adjust the 
desired air/fuel ratio rich and lean to get the oxygen sensor to "switch" around the stoichiometric point. If the 
time between switches are the same, then the system is actually operating at stoichiometry. The desired air/fuel 
control parameter is called short term fuel trim (SHRTFT1 and 2) where stoichiometry is represented by 0 
percent. Richer (more fuel) is represented by a positive number and leaner (less fuel) is represented by a 
negative number. Normal operating range for short term fuel trim is plus or minus 25 percent. Some calibrations 
will have time between switches and short term fuel trim excursions that are not equal. These unequal 
excursions are used to run the system slightly lean or rich of stoichiometry. This practice is referred to as using 
"bias". For example, the fuel system can be biased slightly rich during closed loop fuel to help reduce NOx. 

Values for SHRTFT1 and 2 may change a great deal on a scan tool when the engine is operated at different 
RPM and load points. This is because SHRTFT1 and 2 will react to fuel delivery variability that can change as a 
function of engine RPM and load. Short term fuel trim values are not retained after the engine is turned off. 

Long Term Fuel Trim. While the engine is operating in closed loop fuel, the short term fuel trim corrections can 
be "learned" by the PCM as long term fuel trim (LONGFT1 and 2) corrections. These corrections are stored in 

exceeded during WOT operation. At WOT, injectors will function for a limited 
amount of time allowing customer to complete a passing maneuver.

 

2003 Ford Pickup F150 

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