Check Engine/Mil Description/Operation/Application (88-5-7)

CHECK ENGINE/MIL DESCRIPTION/OPERATION/APPLICATION

TECHNICAL SERVICE BULLETIN

LAMP - "MALFUNCTION INDICATOR LIGHT" (MIL) - SERVICE INFORMATION

APPLICATION

Model: 1988 Ford All Car Lines

1988 Lincoln-Mercury All Car Lines

1988 Merkur All Car Lines

1988 Ford Light Truck All Light Truck Lines

Group: Electrical

Bulletin No.: 88-5-7

Date: March 2, 1988

ISSUE

The Malfunction Indicator Light (MIL) is a new feature that has been added to 1988 vehicles. The MIL (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.

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. This TSB 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.

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.

NON-EEC IV VEHICLES

The Malfunction Indicator Light (MIL) alerts the customer that 60,000 mile emission system maintenance is required.

1988 Vehicles With EEC IV - MIL System Faults	Continuous Error Codes
ECT Engine Coolant Temperature	51, 61
ACT Air Charge Temperature	54, 64
BP Barometric Pressure	22
MAP Manifold Absolute Pressure	22
VAF Vane Air Flow	56, 66
MAF Mass Air Flow	56, 66
EGO, HEGO Exhaust Gas O2	41, 42, 91
PFE Pressure Feedback EGR	31, 35
EVP EGR Valve Position	31, 35
TP Throttle Position	53, 63
ITS Idle Tracking Switch	71
VAT Vane Air Temperature	58, 68
If D.C. motor does not follow dashpot profile	13

Engine	California	49S	Vehicle
1.9L EFI	Yes	No	Escort
1.9L CFI	Yes	No	Escort
2.3L TC	Yes	Yes	Thunderbird/Cougar
2.3L TC	No	No	XR4Ti
2.3L OHC	Yes	Yes	Mustang
2.3L OHC	No	No	Ranger
2.3L HSC	Yes	Yes	Tempo/Topaz
2.5L HSC	Yes	Yes	Taurus/Sable
2.9L EFI	Yes	Yes	Ranger/Bronco II
2.9L EFI	Yes	Yes	Scorpio
3.0L EFI	Yes	Yes	Taurus/Sable
3.0L EFI	Yes	Yes	Aerostar
3.8L FWD	Yes	Yes	Taurus/Sable
3.8L FWD	Yes	No	Continental
3.8L RWD	Yes	Yes	Thunderbird/Cougar
4.9L EFI	Yes	Yes	F-Series/Bronco Econoline
5.0L EFI	Yes	Yes	F-Series/Bronco Econoline
5.0L Mass Air	Yes	---	Mustang
5.0L SFI	---	Yes	Mustang
5.0L SFI	Yes	No	Lincoln Town Car
5.0L SFI	Yes	No	Mark VII
5.0L SFI	Yes	No	Crown Victoria/ Grand Marquis
5.0L SFI	Yes	No	Thunderbird/Cougar
5.8L EFI	Yes	Yes	F-Series/Bronco Econoline
7.5L EFI	Yes	Yes	F-Series, Econoline

NON EEC EQUIPPED VEHICLES

• 1.3L Festiva
• 1.6L Tracer
• 2.0L Ranger
• 6.1 L and 7.0L Gasoline Engines (Truck Applications)