Continuous Memory Codes
These codes are retained in memory for 40 warm-up cycles. To clear the codes for purposes of testing or confirming repair, perform the code reading procedure. When the fault codes begin to be displayed, de-activate the test either by disconnecting the jumper wire (if using a meter, MIL or message center) or by 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 emission 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 (16 km) 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 Link Connector
With the advent of OBD-II, the Federal Government has mandated the location of the DLC (Data Link Connector) .The Data Link Connector is located in the passenger compartment. It is attached to the instrument panel and accessible from the driver's seat.
The DLC is rectangular in design and capable of allowing access to 16 terminals. The connector has keying features that allow easy connection. The test equipment and the DLC have a latching feature to ensure a good mated connection. The Scan tool uses the DLC as a pathway to communicate with the on board computer system.
If the DLC is not located under the dash, the vehicle is using OBD-I. This is a slightly different management system in its operation and diagnosis. Look for DLC under the hood near the left front headlight on the Town Car and Mark VII, near the right side firewall on the Continental.Electrical Tools
The most commonly required electrical diagnostic tool is the digital multimeter; also known as a Digital Volt Ohmmeter (DVOM), which permits voltage, resistance (ohms) and amperage to be read by one instrument.
The multimeter must be a high impedance unit, with 10 megaohms of impedance in the voltmeter. This type of meter will not place an additional load on the circuit it is testing; this is extremely important in low voltage circuits. The multimeter must be of high quality in all respects. It should be handled carefully and protected from impact or damage. Replace the batteries frequently in the unit.
Additionally, an analog (needle type) voltmeter may be used to read stored fault codes if the STAR tester is not available. The codes are transmitted as visible needle sweeps on the face of the instrument.
Nearly all the diagnostic procedures will require the use of a Breakout Box, a device that connects into the EEC-IV harness and provides testing ports for the 60 wires in the harness. Direct testing of the harness connectors at the terminals or by backprobing is not recommended; damage to the wiring and terminals are almost certain to occur.
Other necessary tools include a quality tachometer with inductive (clip-on) pickup, a fuel pressure gauge with system adapters and a vacuum gauge with an auxiliary source of vacuum.Hand-Held Scan Tools
Although stored codes may be read through the flashing of the CHECK ENGINE or SERVICE ENGINE SOON lamp, the use of hand-held scan tools such as Ford's Self-Test Automatic Readout (STAR) tester or the second generation SUPER STAR II tester or their equivalent is highly recommended. There are many manufacturers of these tools; the purchaser must be certain that the tool is proper for the intended use.
The scan tool allows any stored faults to be read from the engine controller memory. Use of the scan tool provides additional data during troubleshooting, but does not eliminate the use of the charts. The scan tool makes collecting information easier, but an operator familiar with the system must correctly interpret the data.
The Powertrain Control Module (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-IV 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.Failure Mode Effects Management (Fmem)
The PCM contains back-up programs that allow the engine to operate if a sensor signal is lost. If 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.
If a code was set before a problem self-corrected (such as a momentarily loose connector), the code will be erased if the problem does not reoccur within 80 warm-up cycles. Codes will be output and displayed as numbers on the hand-held scan tool, such as 23. If the codes are being read on an analog voltmeter, the needle sweeps indicate the code digits. code 23 will appear as two needle pulses (sweeps) then, after a 1.6 second pause, the needle will pulse (sweep) three times.Key On Engine Off (KOEO) Test
- Connect the scan tool to the self-test connectors. Make certain the test button is unlatched or up.
- Start the engine and run it until normal operating temperature is reached.
- Turn the engine OFF for 10 seconds.
- Activate the test button on the STAR tester.
- Turn the ignition switch ON but do not start the engine.
- The KOEO codes will be transmitted. Six to nine seconds after the last KOEO code, a single separator pulse will be transmitted. Six to nine seconds after this pulse, the codes from the Continuous Memory will be transmitted.
- Record all service codes displayed. Do not depress the throttle on gasoline engines during the test.
- Make certain the self-test button is released or de-activated on the STAR tester.
- Start the engine and run it at 2000 rpm for two minutes. This action warms up the oxygen sensor.
- Turn the ignition switch OFF for 10 seconds.
- Activate or latch the self-test button on the scan tool.
- Start the engine. The engine identification code will be transmitted. This is a single digit number representing 1 / 2 the number of cylinders in a gasoline engine. On the STAR tester, this number may appear with a zero, such as 20 = 2. The code is used to confirm that the correct processor is installed and that the self-test has begun.
- If the vehicle is equipped with a Brake On/Off (BOO) switch, the brake pedal must be depressed and released after the ID code is transmitted.
- If the vehicle is equipped with a Power Steering Pressure Switch (PSPS), the steering wheel must be turned at least 1 / 2 turn and released within 2 seconds after the engine ID code is transmitted.
- Certain Ford vehicles will display a Dynamic Response code 6 -20 seconds after the engine ID code. This will appear as one pulse on a meter or as a 10 on the STAR tester. When this code appears, briefly take the engine to wide-open throttle. This allows the system to test the throttle position, MAF and MAP sensors.
- All relevant codes will be displayed and should be recorded. Remember that the codes refer only to faults present during this test cycle. Codes stored in Continuous Memory are not displayed in this test mode.
- Do not depress the throttle during testing unless a dynamic response code is displayed.
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 (STI) 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; for example, 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.Other Test Modes
Continuous Monitor Or Wiggle Test
Once entered, this mode allows the operator to attempt to recreate intermittent faults by wiggling or tapping components, wiring or connectors. The test may be performed during either KOEO or KOER procedures. The test requires the use of either an analog voltmeter or a hand-held scan tool.
To enter the continuous monitor mode during KOEO testing, turn the ignition switch ON . Activate the test, wait 10 seconds, then deactivate, and reactivate the test; the system will enter the continuous monitor mode. Tap, move, or wiggle the harness, component or connector suspected of causing the problem; if a fault is detected, the code will store in the memory. When the fault occurs, the dash-warning lamp will illuminate, the STAR tester will light a red indicator (and possibly beep) and the analog meter needle will sweep once.
To enter this mode in the KOER test:
- Start the engine and run it at 2000 rpm for two minutes. This action warms up the oxygen sensor.
- Turn the ignition switch OFF for 10 seconds.
- Start the engine.
- Activate the test, wait 10 seconds, then deactivate, and reactivate the test; the system will enter the continuous monitor mode.
- Tap, move, or wiggle the harness, component or connector suspected of causing the problem; if a fault is detected, the code will store in the memory.
- When the fault occurs, the dash-warning lamp will illuminate, the STAR tester will light a red indicator (and possibly beep) and the analog meter needle will sweep once.
This testing mode allows the operator to energize and de-energize most of the outputs controlled by the EEC-IV system. Many of the outputs may be checked at the component by listening for a click or feeling the item move or engage by a hand placed on the case. To enter this check:
- Enter the KOEO test mode.
- When all codes have been transmitted, depress the accelerator all the way to the floor and release it.
- The output actuators are now all ON. Depressing the throttle pedal to the floor again switches the all the actuator outputs OFF.
- This test may be performed as often as necessary, switching between ON and OFF by depressing the throttle.
- Exit the test by turning the ignition switch OFF , detaching the jumper at the diagnostic connector or releasing the test button on the scan tool.
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 + lead of the meter to the battery positive terminal and connect the -; lead of the meter to the self-test output pin of the diagnostic connector.
Follow the directions given previously for performing the KOEO and KOER tests. To activate the tests, 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 KOEO codes by 6 seconds, a single sweep and another 6-second delay.Visual Inspection
This is possibly the most critical step of diagnosis. A detailed examination of all connectors, wiring and vacuum hoses can often lead to a repair without further diagnosis. Performance of this step relies on the skill of the technician performing it; a careful inspector will check the undersides of hoses as well as the integrity of hard-to-reach hoses blocked by the air cleaner or other components. Wiring should be checked carefully for any sign of strain, burning, crimping or terminal pullout from a connector.
Checking connectors at components or in harnesses is required; usually, pushing them together will reveal a loose fit. Pay particular attention to ground circuits, making sure they are not loose or corroded. Remember to inspect connectors and hose fittings at components not mounted on the engine, such as the evaporative canister or relays mounted on the fender aprons. Any component or wiring near a fluid leak or spillage should be given extra attention during inspection.
Additionally, inspect maintenance items such as belt condition and tension, battery charge and condition and the radiator cap carefully. Any of these very simple items may affect the system enough to set a fault.