Jumper Wire for EEC Self-Test (WPT-743 & WPT-352)
For more info, read the 7th post in this thread:
http://www.fordf150.net/forums/viewtopic.php?t=71346--------------------------------------------------------------------------------
TSB 88-05-07 MIL Introduction
Publication Date: MARCH 2, 1988
FORD: 1988 ALL CAR LINES
LINCOLN-MERCURY: 1988 ALL CAR LINES
MERKUR: 1988 ALL CAR LINES
LIGHT TRUCK: 1988 ALL LIGHT TRUCK LINES
ISSUE: The Malfunction Indicator Light (MIL) is a new feature that has been added to 1988 vehicles. Vehicle applications follow. The MIL's (Check Engine) is active when the engine system requires service. An explanation of how and when the Malfunction Indicator Light (MIL) operates may need to be explained to some vehicle owners.
ACTION: Use the following service information to explain the operation of the Malfunction Indicator Light (MIL) to resolve customer concerns.
NOTE: IT IS NOT NECESSARY TO IMMEDIATELY TURN OFF THE ENGINE OR HAVE THE VEHICLE TOWED WHEN THE "CHECK ENGINE" (MIL) LIGHT COMES ON.
Vehicles Equipped with EEC IV
The CHECK ENGINE light will come on while engine is operating in Failure Mode Effects Management (FMEM) or Hardware Limited Operation Strategy (HLOS) modes. The light will stay on as long as the fault causing it is present.
In FMEM mode, the computer is receiving a sensor signal that is outside the limits set by the calibration strategy. In this mode, the computer uses an alternate strategy to maintain reasonable vehicle operation in spite of the fault. The following chart lists the system faults which will turn on the CHECK ENGINE light in this mode. The error code associated with this system fault is stored in Keep Alive Memory (KAM). If the fault is no longer present, the light will turn off and vehicle will return to normal vehicle strategy. The error code stored when the light was on was not erased. This code is one of the continuous error codes and can be accessed by running the KOEO self-test.
HLOS mode is used when the system fault(s) is too extreme for the FMEM mode to handle. In HLOS mode, all software operations have stopped and the computer is running on hardware control only. The default strategy for this mode has a minimal calibration just to allow the vehicle to operate until it can be serviced.
NOTE: IN HLOS MODE YOU WILL NOT GET ERROR CODES.
The MIL light is turned on as a bulb check when the ignition key is first turned "ON". The EEC IV computer turns off the bulb as soon as it receives the PIP (crank) signal. If the light stays on during cranking, the computer is not receiving the PIP signal.
To service a MIL concern, use the 1988 Engine/Emission Diagnosis Shop Manual, Volume H, Section 16. If the vehicle has no drive problems, the MIL is on, and no codes are found in memory, follow diagnostics by symptom in the 1988 Engine/Emission Diagnosis Shop Manual, Volume H, Sections 17 or 18.
Non-EEC IV Vehicles
The Malfunction Indicator Light (MIL) alerts the customer that 60,000 mile emission system maintained is required. To service a MIL concern on a non-EEC IV vehicle, refer to the 1988 Engine/Emission Diagnostic Shop Manual, Volume H, Section 13.
OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: INFORMATION ONLY
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Pulling EEC-IV codes ('84-95 EFI)
(This is from the Ford Service CD, but I've edited & reorganized it so it's easier to follow. I deleted the info about the STAR testers since I doubt anyone has one and doesn't know how to use it.)
Self-Test Description
The Self-Test is divided into three specialized tests: Key On Engine Off Self-Test, Engine Running Self-Test, and Continuous Self-Test. The Self-Test is not a conclusive test by itself, but is used as a part of the functional Quick-Test diagnostic procedure. The PCM stores the Self-Test program in permanent memory. When activated, Self-Test checks the EEC system by testing memory integrity and processing capability, and verifies that various sensors and actuators are connected and operating properly.
Continuous Self-Test
· Continuous Memory DTCs are issued as a result of information stored during Continuous Self-Test, while the vehicle was in normal operation. These DTCs are displayed only during Key On Engine Off Self-Test and after the separator pulse. Intermittent faults that have not occurred in the last 80 warm-up cycles (40 cycles on some applications) are erased from Continuous Memory and will not produce a Continuous Memory DTC.
· During this mode of testing the PCM continuously monitors inputs for opens and shorts. The Continuous Memory DTCs must be retrieved within 40 (for some applications) or 80 engine temperature warm up cycles. On the 41st or 81st Engine Temperature cycle, the DTC will be automatically erased. The Continuous Memory DTCs can also be erased by deactivating Self-Test while the DTCs are being outputted.
The Key On Engine Off and Engine Running Self-Tests are functional tests which only detect faults present at the time of the Self-Test. Continuous Self-Test is performed during normal vehicle operation and stores any fault information in Keep Alive Memory (KAM) for retrieval at a later time.
Special Notes:
· The Key On Engine Off and Engine Running Self-Tests detect faults that are present at the time of testing. Faults that occur only when the vehicle is operating or intermittent faults that have occurred in the last 80 warm-up cycles are detected during Continuous Self-Test, stored in Continuous Memory and displayed during Key On Engine Off Self-Test.
· When directed to a Pinpoint Test, always read the cover page(s) for special notes and look carefully at the Pinpoint Test Schematic.
· After service, rerun Quick Test to ensure that service was effective.
· It may be necessary to disconnect or disassemble harness connector assemblies to do some of the inspections. Pin locations should be noted before disassembly.
Visual Check
1. Inspect the air cleaner and inlet ducting.
2. Check all engine vacuum hoses for damage, leaks, cracks, blockage, proper routing, etc.
3. Check EEC system wiring harness for proper connections, bent or broken pins, corrosion, loose wires, proper routing, etc.
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 QUICK TEST.
Vehicle Preparation
1. Perform ALL safety steps required to start and run vehicle tests - apply parking brake, put shift lever firmly in PARK position (NEUTRAL on manual transmission), block drive wheels, etc.
2. Turn off ALL electrical loads--radios, lights, A/C, heater, blower, fans, etc.
Using an Analog Volt/Ohm Meter (VOM)
1. Turn the ignition key off.
2. Set the VOM on a DC voltage range to read from 0 to 15 volts.
3. Connect the VOM from the battery positive post to the Self-Test Output pin of the large Data Link Connector (DLC) (Figure 3).
4. Connect the timing light.
Using the Malfunction Indicator Lamp (MIL)
No special equipment hookup is required. STI is jumpered to SIG RTN at Self-Test Input (STI) connector and the Data Link Connector (DLC). This is where you can use a paperclip.
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Using the Message Center on Continental Applications Only
No special equipment hookup is required. STI is jumpered to SIG RTN at Self-Test Input (STI) connector and the Data Link Connector (DLC).
Using the Transmission Control Indicator Lamp (TCIL) on 7.3L Diesel Engines Only
No special equipment hookup is required. STI is jumpered to SIG RTN at Self-Test Input (STI) connector and the Data Link Connector (DLC).
Key On Engine Off Self-Test
At this time, a test of the EEC system is conducted with power applied and engine at rest. To detect errors during Key On Engine Off Self-Test, the fault must be present at the time of testing.
Special Notes:
· Continuous Memory Diagnostic Trouble Codes (DTCs) recorded in this step will be used for diagnosis after a PASS code 11 or 111 is received in both the Key On Engine Off and the Engine Running Self-Tests.
· Deviation from this procedure may cause the output of false DTCs.
· On all vehicles equipped with a 4.9L ENGINE, the clutch must be depressed during the Key On Engine Off Self-Test.
· On all vehicles equipped with a 7.3L DIESEL ENGINE, the throttle must be depressed (WOT) during the entire Key On Engine Off Self-Test.
How To Run The Key On Engine Off Self-Test
DO:
· Verify that the vehicle has been properly prepared.
· Start engine and run until it reaches operating temperature.
· Turn engine off and wait 10 seconds.
· Activate Self-Test.
. . Analog VOM: Jumper STI to SIG RTN at the DLC and STI connectors.
. . Malfunction Indicator Lamp (MIL): Jumper STI to SIG RTN at the DLC and STI connectors. DTCs will be flashed on the Malfunction Indicator Lamp (MIL).
. . Transmission Control Indicator Lamp (TCIL) 7.3L Diesel only: Jumper STI to SIG RTN at the DLC and STI connectors. Service Codes will be flashed on the TCIL.
. . Message Center (Continental Applications Only). Refer to "Self-Test with Message Center."
· Place ignition key in the ON position.
· For 7.3L Diesel vehicles only, depress the throttle fully, and hold for the entire test.
· Record all Diagnostic Trouble Codes (DTCs) displayed.
DON'T:
· Depress throttle during Key On Engine Off Self-Test on gasoline engine applications.
Separator Pulse
A single 1/2 second separator pulse is issued 6-9 seconds after the last Key On Engine Off DTC. Then, 6-9 seconds after the single 1/2 second separator pulse, the Continuous Memory DTCs will be issued.
NOTE: The separator pulse and Continuous Memory DTCs follow Key On Engine Off DTCs ONLY.
Engine Running Self-Test
At this time, a test of the EEC system is conducted with the engine running. The sensors are checked under actual operating conditions and at normal operating temperatures. The actuators are exercised and checked for expected results.
Special Notes:
· On vehicles equipped with the Brake On/Off (BOO) circuit, the brake pedal MUST be depressed and released AFTER the ID code.
· On vehicles equipped with the Power Steering Pressure (PSP) switch, within 1 to 2 seconds after the ID code, the steering wheel must be turned at least one-half turn and released.
· On vehicles equipped with E4OD transmission, the Transmission Control Switch (TCS) must be cycled after the ID code.
· The Dynamic Response code is a single pulse (or a 10 code on the STAR Tester) that occurs 6-20 seconds after the engine running identification code. (See Code Output Format in this section.)
· When/if the Dynamic Response code occurs, perform a brief wide open throttle.
How To Run Engine Running Self-Test
DO:
· Deactivate Self-Test.
· Start and run engine at 2,000 rpm for two minutes. This action warms up the HO2S.
· Turn engine off, wait 10 seconds.
· Activate Self-Test.
· Start engine.
· After the ID code, depress and release the brake pedal if appropriate. See Special Note on previous page.
· After the ID code, within 1 to 2 seconds, turn the steering wheel at least one-half turn and then release it, if appropriate. See Special Notes above.
· If a Dynamic Response Code occurs, perform a brief wide-open throttle (WOT).
· Record all Diagnostic Trouble Codes (DTCs) displayed.
DON'T:
· Depress the throttle unless a Dynamic Response code is displayed.
Self-Test with Analog Voltmeter
DTCs will be represented by pulsing or sweeping movements of the voltmeter's needle across the dial face of the voltmeter (Figure 9). A single-digit number of three will be reported by three needle pulses (sweeps). However, a DTC is represented by a two-digit or three-digit number, such as 2-3. As a result, the DTC of 2-3 will appear on the voltmeter as two needle pulses (sweeps). After a two-second pause, the needle will pulse (sweep) three times. The Continuous Memory DTCs are separated from the Key On Engine Off DTCs by a six-second delay, a single half-second sweep, and another six-second delay.
Self-Test with Malfunction Indicator Lamp(MIL)
During Self-Test, a DTC is reported by the Malfunction Indicator Lamp (MIL). It will flash the "CHECK ENGINE" or "SERVICE ENGINE SOON" light on the dash panel (Figure 10). A single-digit number of 3 will be reported by three flashes. However, a DTC is represented by two or three digits, such as 2-3 or 1-1-9. As a result, the Self-Test DTC of 2-3 will appear on the MIL as two flashes, then, after a two-second pause, the MIL will flash three times. Three-digit DTCs are flashed out similarly. The Continuous Memory DTCs are separated from the Key On Engine Off DTCs by a six-second delay, a single half-second flash, and another six-second delay.
Self-Test with Message Center (Continental Only)
1. On the Electronic Instrument Cluster (Figure 11), hold in all three buttons (Gauge Select, English Metric and Speed Alarm) at the same time.
a. Key On Engine Off Self-Test: While holding in all three buttons, place ignition switch in the ON position. Release buttons.
b. Key On Engine Running Self-Test: While holding in all three buttons, start engine. Release buttons.
2. Press the Gauge Select button three times, until cluster mode "dEALEr 4" is displayed.
3. To initiate Self-Test, jumper STI to SIG RTN at the DLC and STI connectors.
4. DTC output will be displayed on the message center.
5. To exit Self-Test, turn ignition switch to OFF and remove jumper.
Self-Test with Transmission Control Indicator Lamp (TCIL)
The TCIL serves a dual purpose on the 7.3L Diesel vehicle with E40D transmissions.
· The light stays OFF when the Transmission Control Switch (TCS) is toggled once on the instrument panel--indicating the vehicle can attain the overdrive gear position.
· The light stays ON when the Transmission Control Switch (TCS) is toggled again on the instrument panel--indicating the vehicle is prevented from shifting into the overdrive gear position.
If the light flashes, perform Key On Engine Off Self-Test. The light under this condition serves as a Transmission Malfunction Indicator Lamp. Refer to "Self-Test with Malfunction Indicator Lamp (MIL)" to perform Self-Test.
Code Output Format
The EEC system communicates service information through the Diagnostic Trouble Codes (DTCs). These DTCs are two-digit or three-digit numbers representing the results of Self-Test. The DTCs are transmitted on the Self-Test Output (STO) circuit found in the Data Link Connector (DLC). They are in the form of timed pulses, and are read by the technician on a voltmeter, STAR tester, Malfunction Indicator Lamp (MIL), Transmission Control Indicator Lamp (TCIL) or on the Continental message center.
Fast DTCs/Slow DTCs
Fast DTCs are issued before slow service DTCs. These DTCs contain the identical information as the slow DTCs, but are transmitted at 100 times the normal rate. These DTCs are interpreted by special equipment at the end of the assembly line by the Body and Assembly Division, as well as the SUPER STAR II tester. After Fast DTCs have been output, Self-Test should not be exited (remove jumper, unlatch button, etc.) until all the Slow DTCs have been output. Exiting before slow DTCs have been output will erase any Continuous Memory DTCs. Some meters in service detect these codes as a short burst of information (slight meter deflection).
Engine Identification Codes (ID Codes)
Engine ID codes are issued at the beginning of the Engine Running Self-Test and are one-digit numbers represented by the number of pulses sent out. For gasoline engines, the engine ID code is equal to one-half the number of engine cylinders (i.e. 2 pulses = 4 cylinders). For the 7.3L Diesel engine, the ID code = 5. These codes are used to verify the proper PCM is installed and that the Self-Test has been entered.
Dynamic Response Check
The dynamic response check is used on some applications to verify operation of the TP, MAF, MAP and KS sensors during the brief Wide-Open Throttle (WOT) performed during the Engine Running Self-Test. The signal for the operator to perform the brief WOT is a single pulse or 10 code on the STAR Tester.
Power Steering Pressure (PSP) Switch Test
On vehicles equipped with Power Steering Pressure (PSP) switch, the steering wheel must be turned one-half turn and released AFTER the ID Code has been displayed. This tests the ability of the EEC system to detect a change of state in the PSP switch.
Brake On/Off Test
On vehicles equipped with Brake On/Off (BOO) input, the brake pedal MUST be depressed and released AFTER the ID Code has been displayed. This tests the ability of the EEC system to detect a change of state in the Brake Lamp Switch.
Transmission Control Switch (TCS) Test
On vehicles equipped with TCS, the switch must be cycled after the ID code has been displayed. This tests the ability of the EEC system to detect a change of state in the TCS.
Adaptive Fuel Self-Test
Adaptive fuel logic is used in fuel injection systems primarily to account for normal variability in fuel system components. When the fuel system is detected to be biased rich or lean during steady state vehicle operation, Adaptive Fuel will make a corresponding shift in the fuel delivery calculations so an unbiased condition will exist. The adaptive fuel "shift" is stored in Keep Alive Memory (KAM), which is powered by the vehicle battery. This prevents Adaptive Fuel from being lost when the vehicle is turned off.
MAF/TP/Injector Pulse Width In-Range Self-Test
The In-Range Self-Test was designed to detect in-range failures of the MAF/TP or fuel delivery systems. The PCM will use information from these three systems to generate three independent values. The three independent values will be continuously monitored. If one of the values differ significantly from the others during normal vehicle operation, a Continuous Memory DTC 121, 124, 125, 184, 185, 186 or 187 will be displayed.
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Diagnostic Aids -Continuous Monitor Diagnostic Test Mode (Wiggle Test)
Special Note: The technician can ATTEMPT to re-create and detect an intermittent fault using the Continuous Monitor DTM (Wiggle Test) procedures.
Key On Engine Off Wiggle Test Procedure
1. Hook up a STAR Tester, VOM or Scan Tool.
2. Turn the ignition key to the ON position.
3. For STAR Tester or VOM, activate, deactivate and reactivate Self-Test. You are now in the Continuous Monitor Diagnostic Test Mode (DTM). For Scan Tool, enter DTM, then enter wiggle DTM.
4. Tap, move, and wiggle the suspect sensor and/or harness. When a fault is detected, a Continuous Memory DTC will be stored in memory. This will be indicated as follows depending on the type of equipment being used:
* STAR Tester: Red LED lights and/or continuous tone.
* Malfunction Indicator Lamp (MIL): Lights
* VOM: Needle Sweep
* Transmission Control Indicator Lamp (TCIL)
* Scan Tool: Continuous Tone
Engine Running Wiggle Test Procedure
Special Note: The Engine Running Wiggle Test may be activated any time the engine is running.
1. Hook up a STAR Tester, VOM or Scan Tool.
2. Key off.
3. Start the engine.
4. For STAR Tester or VOM, activate Self-Test, deactivate and reactivate Self-Test. DO NOT shut the engine off. You are now in the Engine Running Continuous Monitor DTM. For Scan Tool, enter DTM, then enter wiggle DTM.
5. Tap, move, and wiggle the suspect sensor and/or harness or drive the vehicle. When a fault is detected, a Continuous Memory DTC will be stored in memory. This will be indicated as follows depending on the type of equipment being used:
* STAR Tester: Red LED lights and/or continuous tone.
* Malfunction Indicator Lamp (MIL): Lights
* VOM: Needle Sweep
* Transmission Control Indicator Lamp (TCIL)
* Scan Tool: Beeps
How to Clear the Continuous Memory
NOTE: Do not disconnect battery to clear Continuous Memory. This will erase the Keep Alive Memory (KAM) information which may cause a driveability concern.
1. Run the Key On Engine Off Self-Test.
2. When the DTC's begin to be displayed, deactivate Self-Test:
-- STAR Tester: Unlatching the center button (up position).
-- All others: Remove the jumper wire from between Self-Test Input (STI) connector and the Signal Return Pin of the DLC.
-- Scan Tool: Pushing the STOP button.
3. Continuous Memory will be erased in the PCM.
NOTE: KOEO & KOER DTCs cannot be cleared except by repairing the fault causing them.
How to Clear Keep Alive Memory (KAM)
The PCM stores information about vehicle operating conditions and uses this information to compensate for component tolerances. When an emission related component is replaced, Keep Alive Memory (KAM) should be cleared to erase the information stored by the PCM from the original component. To clear KAM: Disconnect the negative side of the battery for a minimum of five minutes. After KAM has been cleared, the vehicle may exhibit certain driveability concerns. It will be necessary to drive the vehicle 10 miles or more to allow the processor to relearn values for optimum driveability and performance. (Distance is dependent on the vehicle application.)
Output State Diagnostic Test Mode (DTM)
The Output State DTM aids in servicing output actuators associated with the EEC system. It enables the technician to energize and de-energize most of the system output actuators on command. This DTM is entered after all DTC's have been received from Key On Engine Off and Continuous Testing. At this time, leave Self-Test activated and depress the throttle. Each time the throttle is depressed the output actuators will change state from energized to de-energized or from de-energized to energized.
1. Enter Self-Test.
2. DTC Output Ends.
3. Do Brief WOT.
4. EEC Output To Actuators Energized.
5. Do Brief WOT.
6. EEC Output To Actuators De-Energized.
7. For vehicles with LFC and HFC circuits:
To cycle the LFC and HFC outputs after code output ends, depress and hold throttle. For LFC, wait until the MIL flashes once (10 seconds). For HFC, wait until MIL flashes twice (15 seconds). Release throttle. The LFC or HFC output is now on (to cycle output off, depress and release throttle).
Cylinder Balance DTM--SFI Engines Only (no F-series or Bronco)
The purpose of the cylinder balance test is to assist the mechanic in finding a weak or non-contributing cylinder. The test is entered by depressing and releasing the throttle within two minutes after the Engine Running Self-Test DTC's have been output.
Once the test is entered, the IAC duty cycle is fixed and the engine is allowed to stabilize. Engine rpm is measured and stored for later use. Next, the fuel is shut off to cylinder number 4, 6 or 8, depending on engine. After a brief stabilization period the engine rpm is again measured and stored. The injector is turned on again and the process is repeated for each of the injectors down to one. At this point, the maximum rpm drop that occurred is selected from the table of rpm drops for each cylinder. This maximum rpm drop is now multiplied by a calibratable percentage. The resulting number (rpm) is now used as the minimum rpm that each cylinder must have dropped to pass this test.
Example: 150 rpm x 65% = 98 rpm
If all cylinders drop at least this amount, then a code 90 is output indicating a pass. No further testing is necessary. If a cylinder did not drop at least this amount, then the cylinder number would be output. For example, 30 for cylinder number 3. This indicates that cylinder number 3 is either weak or non-contributing.
The test can now be repeated a second time if the throttle is depressed and released within two minutes of the last code output. This time the maximum rpm drop that occurs is multiplied by a lower percentage. This number is now used as the minimum rpm drop for each cylinder to pass this test.
Example: 150 rpm x 43% = 65 rpm
If all the rpm drops are greater than 65 rpm, then a code 90 is output. If cylinder number 3 had failed the first level and passed the second, then cylinder number 3 is considered to be weak. If cylinder number 3 again failed, the code 30 would be output again.
The test can be repeated a third time by depressing and releasing the throttle within two minutes of the last code output. This time the maximum rpm drop that results is multiplied by a still lower percentage. This number is now used as the minimum rpm drop for each cylinder to pass this test.
Example: 150 rpm x 20% = 30 rpm
If all the rpm drops are greater than 30 rpm then a code 90 is output. If cylinder number 3 had failed the first and second level, but passed the third, then it is considered to be a very weak cylinder. If cylinder number 3 failed the third level then a code 30 would again be output. In this case, cylinder number three would be considered a non-contributing cylinder.
The Cylinder Balance DTM may still be repeated as many times as desired by depressing and releasing the throttle within two minutes of the last code output. All further testing (i.e. 4th, 5th pass) will be done using the third level percentage.
Failure Mode Effects Management (FMEM)
FMEM is an alternate system strategy in the PCM designed to maintain vehicle operation should one or more sensor inputs fail. When a sensor input is perceived to be out-of-limits by the PCM, an alternative strategy will be initiated. The PCM will substitute a fixed in-limit sensor value and will continue to monitor the faulty sensor input. If the faulty sensor operates within limits, the PCM will return to the normal engine running strategy. Engine Running DTC 98 or 998 will be displayed when FMEM is in effect. The Malfunction Indicator Lamp (MIL)/Message will remain on when FMEM is in effect.
Malfunction Indicator Lamp (MIL)--All Applications Except Continental
The Malfunction Indicator Lamp (MIL) is intended to alert the driver of certain malfunctions in the EEC-IV system. The MIL is a light in the dash that reads either "CHECK ENGINE" or "SERVICE ENGINE SOON." If the light is on, the driver of the vehicle should take the car in for service as soon as possible.
NOTE: It is not necessary to immediately turn the engine off and have the vehicle towed when the MIL comes on.
The MIL will come on while the engine is operating in Failure Mode Effects Management (FMEM) or Hardware Limited Operation Strategy (HLOS) modes. The light will stay on for at least 10 seconds, then stay on as long as the fault causing it is present. If the MIL flashes quickly (less than 10 seconds) the MIL circuit should be checked for concerns. Refer to «Quick Test».
In FMEM mode, the PCM is receiving a sensor signal that is outside the limits set by the calibration strategy. In this mode the PCM uses an alternate engine control strategy to maintain reasonable vehicle operation in spite of the fault. The DTC associated with this fault is stored in Keep Alive Memory (KAM). If the fault is no longer present, the light will turn off and the vehicle will return to the normal vehicle strategy. The DTC stored when the light was on is kept in Continuous Memory for the next 80 warm-up cycles (40 cycles on some applications) and then erased. This DTC is one of the Continuous Memory and it can be accessed by running the Key On Engine Off Self-Test.
HLOS mode is used when the system fault(s) is too extreme for the FMEM mode to handle. In HLOS mode, all software operations have stopped and the PCM is running on hardware control only. The default strategy for this mode has a minimal calibration strictly to allow the vehicle to operate until it can be serviced.
NOTE: In HLOS mode Self-Test DTC's will not be output.
How the Malfunction Indicator Lamp (MIL) Operates
System OK: The Malfunction Indicator Lamp (MIL) is turned on as a bulb check when the ignition key is first turned on. The EEC-IV processor turns the bulb off as soon as it receives the PIP (cranking) signal.
System Not OK: If the Malfunction Indicator Lamp (MIL) should remain on after the vehicle has started, run Quick Test and has had service any DTC's. If Self-Test has pass DTC's, the (MIL) is always on, and the vehicle has no drive symptoms, go to «Section 2A».
If the MIL never comes on, go to «Section 2A».
If the vehicle is a no start, go to Pinpoint Test Step «AA1», «AB1», or «AC1».
NOTE: When in Self-Test the MIL is not limited to Continuous Memory Codes and will also flash other DTC's. Also, Continuous Memory Codes are erased from Continuous Memory if the original fault has not occurred in the last 80 warm-up cycles (40 cycles on some applications).
