Engine Controls - Diagnostic Methods (Except Diesel & Hybrid): Other Ford Explorer IV

Vehicle Check/Preparation

Before using the scan tool to carry out any test, refer to the important Safety Notice located at the beginning of this manual and the necessary visual checks listed below.

Visual Checks

1. Inspect the air cleaner and inlet duct.
2. Check all engine vacuum hoses for damage, leaks, cracks, kinks, and proper routing.
3. Check the electronic engine control (EEC) system wiring harness for proper connections, bent or broken pins, corrosion, loose wires, and proper routing.
4. Check the powertrain control module (PCM), sensors, and actuators for physical damage.
5. Check the engine coolant for proper level and mixture.
6. Check the transmission fluid level and quality.
7. Make all necessary repairs before continuing with the quick test. Refer to «QUICK TEST»(ref-268483-S36593804702007102400000) .

Vehicle Preparation

1. Carry out all safety steps required to start and run vehicle tests. Apply the parking brake, place the gear selector lever firmly into the PARK position on automatic transmission vehicles or NEUTRAL on manual transmission vehicles, and block the drive wheels.
2. Turn off all electrical loads such as radios, lamps, A/C, blower, and fans.
3. Start the engine (if the engine runs) and bring it up to the normal operating temperature before running the quick test.

One Touch Integrated Start System

Some vehicles are equipped with one touch integrated start system. It may be necessary to disable the one touch integrated start system to carry out diagnostic procedures that require extended cranking. Connect the scan tool, access the PCM and select the one touch integrated start system control PID to disable the system.

Generic OBD PID List

CL = Closed loop using HO2S(s) as feedback for fuel control.

OL DRIVE = Open loop due to driving conditions (heavy acceleration).

OL FAULT = Open loop due to fault with all upstream HO2S sensors.

CL FAULT = Closed loop fuel control, but fault with one upstream HO2S sensor on dual bank vehicles.

Ford PID List

Note. This is not a complete list of Ford PIDs available.

Making Changes to the VID Block

A PCM which is programmed may require changes to be made to certain VID information to accommodate the vehicle hardware. Refer to Module Reprogramming on the scan tool.

Drive Cycle Recommendations

1. Most OBD monitors complete more readily using a steady foot driving style during cruise or acceleration modes. Operating the throttle in a smooth fashion minimizes the time required for monitor completion.
2. The fuel tank level should be between 1/2 and 3/4 full with 3/4 full being the most desirable.
3. The evaporative monitor can operate only during the first 30 minutes of engine operation. When executing the procedure for this monitor, stay in part throttle mode and drive in a smooth fashion to minimize fuel slosh.
4. When bypassing the EVAP/secondary AIR engine soak times, the PCM must remain powered (key ON) after clearing the continuous DTCs and relearning emission diagnostic information.

For best results, follow each of the following steps as accurately as possible

Recreating the Fault

Recreating the concern is the first step in isolating the cause of the intermittent symptom. A thorough investigation should start with the customer information worksheet . If freeze frame data is available, it may help in recreating the conditions at the time of a malfunction indicator lamp diagnostic trouble code (MIL DTC). Listed below are some of the conditions for recreating the concern

CONDITIONS TO RECREATE FAULT

Accumulating PCM Data

PCM data can be accumulated in a number of ways. This includes circuit measurements with a digital multimeter (DMM) or scan tool parameter identification (PID) data. Acquisition of PCM PID data using a scan tool is one of the easiest ways to gather information. Gather as much data as possible when the concern is occurring to prevent improper diagnosis. Data should be accumulated during different operating conditions and based on the customer description of the intermittent concern. Compare this data with the known good data values located TYPICAL DIAGNOSTIC REFERENCE VALUES . This requires recording data in 4 conditions for comparison: 1) KOEO, 2) Hot Idle, 3) 48 km/h (30 mph), and 4) 89 km/h (55 mph).

Comparing PCM Data

After the PCM values are acquired, it is necessary to determine the concern area. This typically requires the comparison of the actual values from the vehicle to the typical values from the TYPICAL DIAGNOSTIC REFERENCE VALUES . The charts apply to different vehicle applications (engine, model, transmission).

Analyzing PCM Data

Look for abnormal events or values that are clearly incorrect. Inspect the signals for abrupt or unexpected changes. For example, during a steady cruise most of the sensor values should be relatively stable. Sensors such as throttle position (TP), mass air flow (MAF), and RPM that change abruptly when the vehicle is traveling at a constant speed are clues to a possible concern area.

Look for an agreement in related signals. For example, if the APP1, APP2, or APP3, is changed during acceleration, a corresponding change should occur in idle air control (IAC), RPM, and SPARK ADV PID.

Make sure the signals act in proper sequence. An increase in RPM after the TP1 and TP2 is increased is expected. However, if the RPM increases without a TP1 and TP2 change, a concern may exist.

Scroll through the PID data while analyzing the information. Look for sudden drops or spikes in the values.

Obtain Freeze Frame Data

Freeze frame data is helpful in duplicating and diagnosing adaptive fuel concerns. The data (a snapshot of certain parameter identification (PID) values recorded at the time the DTC is stored in Continuous Memory) is helpful to determine how the vehicle was being driven when the concern occurred, and is especially useful on intermittent concerns. Freeze frame data, in many cases, helps to isolate possible areas of concern as well as rule out others. Refer to FREEZE FRAME DATA for a more detailed description of this data.

Using the LONGFT1 and LONGFT2 (Dual Bank Engines) PIDs

The LONGFT1/2 PIDs are useful for diagnosing fuel trim concerns. A negative PID value indicates that fuel is being reduced to compensate for a rich condition. A positive PID value indicates that fuel is being increased to compensate for a lean condition. It is important to know that there is a separate LONGFT value that is used for each RPM/load point of engine operation. When viewing the LONGFT1/2 PIDs, the values may change a great deal as the engine is operating at different RPM and load points. This is because the fuel system may have learned corrections for fuel delivery concerns that can change as a function of engine RPM and load. The LONGFT1/2 PIDs display the fuel trim currently being used at that RPM and load point. Observing the changes in LONGFT1/2 can help when diagnosing fuel system concerns. For example

1. A contaminated mass air flow (MAF) sensor results in matching LONGFT1/2 correction values that are negative at idle (reducing fuel), but positive (adding fuel) at higher RPM and loads.
2. LONGFT1 values that differ greatly from LONGFT2 values rule out concerns that are common for both banks (for example, fuel pressure concerns, MAF sensor, etc. can be ruled out).
3. Vacuum leaks result in large rich corrections (positive LONGFT1/2 value) at idle, but little or no correction at higher RPM and loads.
4. A plugged fuel filter results in no correction at idle, but large rich corrections (positive LONGFT1/2 value) at high RPM and load.

Air Measurement System

With this condition, the engine runs rich or lean of stoichiometry (14.7:1 air/fuel ratio) if the powertrain control module (PCM) is not able to compensate enough to correct for the condition. One possibility is that the mass of air entering the engine is actually greater than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine runs lean at higher RPM because the PCM delivers fuel for less air than is actually entering the engine. Examples

1. The MAF sensor measurement is inaccurate due to a corroded connector, contaminated or dirty connector. A contaminated MAF sensor typically results in a rich system at low airflows (PCM reduces fuel) and a lean system at high airflows (PCM increases fuel).

Vacuum Leaks/Unmetered Air

With this condition, the engine runs lean of stoichiometry (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. This condition is caused by unmetered air entering the engine, or due to a MAF concern. In this situation, the volume of air entering the engine is actually greater than what the MAF sensor is indicating to the PCM. Vacuum leaks are normally most apparent when high manifold vacuum is present (for example, during idle or light throttle). If freeze frame data indicates that the concern occurred at idle, a check for vacuum leaks/unmetered air is the best starting point. Examples

1. loose, leaking, or disconnected vacuum lines
2. intake manifold gaskets, or O-rings
3. throttle body gaskets
4. brake booster
5. air inlet tube
6. stuck/frozen/aftermarket positive crankcase valve (PCV)
7. unseated engine oil dipstick.

Insufficient Fueling

With this condition, the engine runs lean of stoichiometry (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. This condition is caused by a fuel delivery system concern that restricts or limits the amount of fuel being delivered to the engine. This condition is normally apparent as the engine is under a heavy load and at high RPM, when a higher volume of fuel is required. If the freeze frame data indicates that the concern occurs under a heavy load and at higher RPM, a check of the fuel delivery system (checking fuel pressure with engine under a load) is the best starting point. Examples

1. low fuel pressure (fuel pump, fuel filter, fuel leaks, restricted fuel supply lines)
2. fuel injector concerns

Exhaust System Leaks

In this type of condition, the engine runs rich of stoichiometry (14.7:1 air/fuel ratio) because the fuel control system is adding fuel to compensate for a perceived (not actual) lean condition. This condition is caused by oxygen (air) entering the exhaust system from an external source. The HO2S react to this exhaust leak by increasing fuel delivery. This condition causes the exhaust gas mixture from the cylinder to be rich. Examples

1. exhaust system leaks upstream or near the HO2S
2. cracked/leaking HO2S boss
3. inoperative secondary air injection system

With this condition, the engine runs rich or lean of stoichiometry (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. One possibility is that the mass of air entering the engine is actually less than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine runs rich at idle because the PCM delivers fuel for more air than is actually entering the engine. Examples

1. MAF sensor measurement inaccurate due to a corroded connector, contamination/dirt. A contaminated MAF sensor typically results in a rich system at low airflows (PCM reduces fuel) and a lean system at high airflows (PCM increases fuel).

Fuel System

With this condition, the engine runs rich of stoichiometry (14.7:1 air/fuel ratio), if the PCM is not able to compensate enough to correct for the condition. This situation causes a fuel delivery system that is delivering excessive fuel to the engine.

Examples

1. fuel pressure regulator causes excessive fuel pressure (system rich at all airflows), fuel pressure is intermittent, going to pump deadhead pressure, then returning to normal after the engine is turned off and restarted.
2. fuel pulse dampener diaphragm ruptured (fuel leaking into the intake manifold, system rich at lower airflows).
3. fuel injector leaks (injector delivers extra fuel).
4. EVAP canister purge valve leak (if the canister is full of vapors, introduces extra fuel).
5. fuel rail pressure (FRP) sensor (electronic returnless fuel systems) concern causes the sensor to indicate a lower pressure than actual. The PCM commands a higher duty cycle to the fuel pump driver module (FPDM), causing high fuel pressure (system rich at all airflows).

Air Inlet System

A restriction within any of the following components may be significant enough to affect the ability of the PCM adaptive fuel control.

1. air inlet tube
2. air cleaner element
3. air cleaner assembly
4. resonators
5. clean air tube

Base Engine

Engine oil contaminated with fuel can contribute to a rich-running engine.