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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
by Ford via Steve83
