1991 1999 ford explorer chilton User Manual

							5.0L ENGINE (1 OF 3)
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HOW TO USE THIS BOOK
COMPONENT LOCATIONS 577 
						

							5.0L ENGINE (2 OF 3)
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HOW TO USE THIS BOOK
578 COMPONENT LOCATIONS 
						

							5.0L ENGINE (3 OF 3)
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Chilton® Automotive Information Systems. © 2004 Thomson Delmar Learning. HOW TO USE THIS BOOK
COMPONENT LOCATIONS 579 
						

							
TROUBLE CODES
General Description
Ford Ranger/Explorer and Mountaineer vehicles employ the Electronic Engine Control (EEC) system, to
manage fuel, ignition and emissions on vehicle engines.
The Powertrain Control Module (PCM) is given responsibility for the operation of the emission control
devices, cooling fans, ignition and advance and in some cases, automatic transmission functions. Because the
EEC oversees both the ignition timing and the fuel injector operation, a precise air/fuel ratio will be
maintained under all operating conditions. The PCM is a microprocessor or small computer which receives
electrical inputs from several sensors, switches and relays on and around the engine.
Based on combinations of these inputs, the PCM controls outputs to various devices concerned with engine
operation and emissions. The engine control assembly relies on the signals to form a correct picture of current
vehicle operation. If any of the input signals is incorrect, the PCM reacts to what ever picture is painted for it.
For example, if the coolant temperature sensor is inaccurate and reads too low, the PCM may see a picture of
the engine never warming up. Consequently, the engine settings will be maintained as if the engine were cold.
Because so many inputs can affect one output, correct diagnostic procedures are essential on these systems.
One part of the PCM is devoted to monitoring both input and output functions within the system. This ability
forms the core of the self-diagnostic system. If a problem is detected within a circuit, the controller will
recognize the fault, assign it an identification code, and store the code in a memory section. Depending on the
year and model, the fault code(s) may be represented by two or three digit numbers. The stored code(s) may
be retrieved during diagnosis.
While the EEC system is capable of recognizing many internal faults, certain faults will not be recognized.
Because the computer system sees only electrical signals, it cannot sense or react to mechanical or vacuum
faults affecting engine operation. Some of these faults may affect another component which will set a code.
For example, the PCM monitors the output signal to the fuel injectors, but cannot detect a partially clogged
injector. As long as the output driver responds correctly, the computer will read the system as functioning
correctly. However, the improper flow of fuel may result in a lean mixture. This would, in turn, be detected by
the oxygen sensor and noticed as a constantly lean signal by the PCM. Once the signal falls outside the
pre-programmed limits, the engine control assembly would notice the fault and set an identification code.
Additionally, the EEC system employs adaptive fuel logic. This process is used to compensate for normal
wear and variability within the fuel system. Once the engine enters steady-state operation, the engine control
assembly watches the oxygen sensor signal for a bias or tendency to run slightly rich or lean. If such a bias is
detected, the adaptive logic corrects the fuel delivery to bring the air/fuel mixture towards a centered or 14.7:1
ratio. This compensating shift is stored in a non-volatile memory which is retained by battery power even
with the ignition switched OFF. The correction factor is then available the next time the vehicle is operated.
If the battery cable(s) is disconnected for longer than 5 minutes, the adaptive fuel factor will be lost.
After repair it will be necessary to drive the truck at least 10 miles to allow the processor to relearn the
correct factors. The driving period should include steady-throttle open road driving if possible. During
the drive, the vehicle may exhibit driveability symptoms not noticed before. These symptoms should
clear as the PCM computes the correction factor. The PCM will also store Code 19 indicating loss of
power to the controller.
TROUBLE CODES 581 
						

							
FAILURE MODE EFFECTS MANAGEMENT (FMEM)
The engine controller assembly contains back-up programs which allow the engine to operate if a sensor
signal is lost. If a sensor input is seen to be out of range-either high or low-the FMEM program is used. The
processor substitutes a fixed value for the missing sensor signal. The engine will continue to operate, although
performance and driveability may be noticeably reduced. This function of the controller is sometimes referred
to as the limp-in or fail-safe mode. If the missing sensor signal is restored, the FMEM system immediately
returns the system to normal operation. The dashboard warning lamp will be lit when FMEM is in effect.
HARDWARE LIMITED OPERATION STRATEGY (HLOS)
This mode is only used if the fault is too extreme for the FMEM circuit to handle. In this mode, the processor
has ceased all computation and control; the entire system is run on fixed values. The vehicle may be operated
but performance and driveability will be greatly reduced. The fixed or default settings provide minimal
calibration, allowing the vehicle to be carefully driven in for service. The dashboard warning lamp will be lit
when HLOS is engaged. Codes cannot be read while the system is operating in this mode.
MALFUNCTION INDICATOR LAMP (MIL)
The CHECK ENGINE or SERVICE ENGINE SOON dashboard warning lamp is referred to as the
Malfunction Indicator Lamp (MIL). The lamp is connected to the engine control assembly and will alert the
driver to certain malfunctions within the EEC system. When the lamp is lit, the PCM has detected a fault and
stored an identity code in memory. The engine control system will usually enter either FMEM or HLOS mode
and driveability will be impaired.
The light will stay on as long as the fault causing it is present. Should the fault self-correct, the MIL will
extinguish but the stored code will remain in memory.
Under normal operating conditions, the MIL should light briefly when the ignition key is turned ON. As soon
as the PCM receives a signal that the engine is cranking, the lamp will be extinguished. The dash warning
lamp should remain out during the entire operating cycle.
Diagnostic Connector
To read Diagnostic Trouble Codes (DTCs) the test connector for the EEC system must be used. This
connector is known as the Assembly Line Diagnostic Link (ALDL) connector on vehicles with EEC-IV
ignition equipped engines, or the Data Link Connector (DLC) on all other models (EEC-V), is located in the
passenger compartment. It is attached either to the underside of the instrument panel, and is accessible from
the drivers side of the vehicle, or it is under the hood near the power distribution box.
The connector is trapezoidal in shape and can accommodate up to 16 terminals. HOW TO USE THIS BOOK
582 FAILURE MODE EFFECTS MANAGEMENT (FMEM) 
						

							To access the diagnostic connector, unfasten it from its protective cover, which is labeled EEC
TEST
Reading Codes
Inexpensive scan tools, such as this Auto Xray®, are available to interface with your Ford vehicle
HOW TO USE THIS BOOK
Diagnostic Connector 583 
						

							When using a scan tool, make sure to follow all of the manufacturers instructions carefully to
ensure proper diagnosis
EEC-V EQUIPPED ENGINES
The EEC-V equipped engines utilize On Board Diagnostic II (OBD-II) Diagnostic Trouble Codes (DTCs),
which are alpha-numeric (they use letters and numbers). The letters in the OBD-II DTCs make it highly
difficult to convey the codes through the use of anything but a scan tool. Therefore, to read the OBD-II DTCs
on these vehicles it is necessary to utilize an OBD-II compatible scan tool.
Ensure that the ignition switch is in the OFFposition.
1. 
Apply the parking brake.
2. 
Ensure that transmission gearshift is in either Park (automatic transmissions) or Neutral (manual
transmissions).
3. 
Block the rear wheels.
4. 
Turn off all electrical loads, such as the heater blower motor, the radio, the rear defroster, etc.
5. 
Connect the scan tool to the Data Link Connector (DLC-3.8L and 4.6L engines) or the Assembly
Line Diagnostic Link (ALDL-5.0L engine). Make certain the test button on the scan tool is unlatched
or up.
6. 
Turn the ignition switch to the ONposition without starting the engine (KOEO).
7. 
Using the scan tool, retrieve and record any continuous memory DTCs.
8. 
Turn the ignition switch to the OFFposition.
9. 
Start the engine and run it until normal operating temperature is reached.
10. 
Turn the engine OFFand wait 10 seconds.
11. 
Turn the ignition switch ONbut do not start the engine.
12. 
Activate the KOEO self-test. Retrieve and record any KOEO DTCs after the KOEO test is complete.
13. 
Ignore DTC 1000. If any DTCs were present, refer to the accompanying OBD-II charts to locate the problem(s).
14. 
EEC-IV EQUIPPED ENGINES
The EEC-IV equipped engines use an older diagnostic system to monitor and report engine related
malfunctions. This older system is known as On Board Diagnostics (OBD-I). The Diagnostic Trouble Codes HOW TO USE THIS BOOK
584 Reading Codes 
						

							
(DTCs) are two or three digit numbers, and can be read through the use of a scan tool, an analog voltmeter, or
with the Malfunction Indicator Lamp (MIL) located on the instrument cluster. Use the accompanying OBD-I
DTC charts to decipher the DTCs for the identification of the malfunctioning component or circuit.
Scan Tool Method Connect the scan tool to the self-test connectors. Make certain the test button is unlatched or up.
1. 
Start the engine and run it until normal operating temperature is reached.
2. 
Turn the engine OFFand wait 10 seconds.
3. 
Activate the test button on the STAR tester.
4. 
Turn the ignition switch ONbut do not start the engine.
5. 
The codes will be transmitted. Six to nine seconds after the last code, a single separator pulse will be
transmitted. Six to nine seconds after this pulse, the codes from the Continuous Memory will be
transmitted.
6. 
Record all service codes displayed. Do not depress the throttle during the test.
7. 
Afdter the test, compare the DTCs retrieved with the accompanying OBD-I code identification charts
in the Specifications Charts.
8. 
Analog Voltmeter Method
In the absence of a scan tool, an analog voltmeter may be used to retrieve stored fault codes. Set the meter
range to read DC 0-15 volts. Connect the positive lead of the meter to the battery positive terminal and
connect the negative lead of the meter to the Self-Test Output (STO) pin of the diagnostic connector.
Follow the directions given previously for performing the scan tool procedure. To activate the procedure, use
a jumper wire to connect the signal return pin on the diagnostic connector to the self-test input connector. The
self-test input line is the separate wire and connector with or near the diagnostic connector.
The codes will be transmitted as groups of needle sweeps. This method may be used to read either 2 or 3 digit
codes. The Continuous Memory codes are separated from the other codes by 6 seconds, a single sweep and
another 6 second delay.
After the test, compare the DTCs retrieved with the accompanying OBD-I code identification charts
in the Specifications Charts.
1. 
Malfunction Indicator Lamp (MIL) Method
The Malfunction Indicator Lamp (MIL) on the dashboard may also be used to retrieve the stored codes. This
method displays only the stored codes and does not allow any system investigation. It should only be used in
field conditions where a quick check of stored codes is needed.
Follow the directions given previously for performing the scan tool procedure. To activate the tests, use a
jumper wire to connect the signal return pin on the diagnostic connector to the Self-Test Input (STO)
connector. The self-test input line is the separate wire and connector with or near the diagnostic connector.
Codes are transmitted by place value with a pause between the digits; Code 32 would be sent as 3 flashes, a
pause and 2 flashes. A slightly longer pause divides codes from each other. Be ready to count and record
codes; the only way to repeat a code is to recycle the system. This method may be used to read either 2 or 3
digit codes. The Continuous Memory codes are separated from the other codes by 6 seconds, a single flash
and another 6 second delay. HOW TO USE THIS BOOK
EEC-IV EQUIPPED ENGINES 585 
						

							
Clearing Codes
CONTINUOUS MEMORY CODES
These codes are retained in memory for 40 warm-up cycles. To clear the codes for the purposes of testing or
confirming repair, perform the code reading procedure. When the fault codes begin to be displayed,
de-activate the test by either disconnecting the jumper wire (meter, MIL or message center) or releasing the
test button on the hand scanner. Stopping the test during code transmission will erase the Continuous
Memory. Do not disconnect the negative battery cable to clear these codes; the Keep Alive memory will be
cleared and a new code, 19, will be stored for loss of PCM power.
KEEP ALIVE MEMORY
The Keep Alive Memory (KAM) contains the adaptive factors used by the processor to compensate for
component tolerances and wear. It should not be routinely cleared during diagnosis. If an emissions related
part is replaced during repair, the KAM must be cleared. Failure to clear the KAM may cause severe
driveability problems since the correction factor for the old component will be applied to the new component.
To clear the Keep Alive Memory, disconnect the negative battery cable for at least 5 minutes. After the
memory is cleared and the battery reconnected, the vehicle must be driven at least 10 miles so that the
processor may relearn the needed correction factors. The distance to be driven depends on the engine and
vehicle, but all drives should include steady-throttle cruise on open roads. Certain driveability problems may
be noted during the drive because the adaptive factors are not yet functioning.
Diagnostic Trouble Code Charts HOW TO USE THIS BOOK
586 Clearing Codes 
						

							OBD-II DIAGNOSTIC TROUBLE CODE (DTC) APPLICATIONS
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Diagnostic Trouble Code Charts 587