MIL Lamp
Notice: If the vehicle is continually driven when the MIL lamp is activated, the emission controls may not work as well, the vehicle fuel economy may not be as good, and the engine may not run as smoothly. This could lead to costly repairs that may not be covered by the vehicle warranty.
Modifications made to the engine, transmission, exhaust, intake, or fuel system of the vehicle, or replacing the original tires with tires that do not meet the same tire performance criteria, can affect the vehicle's emission controls and can cause the MIL lamp to activate. Modifications to these systems could lead to costly repairs not covered by the vehicle warranty. This could also result in a failure to pass required emission inspection and/or maintenance tests.
When the MIL lamp activates, it can either flash on and off, or remain on with a constantly illuminated lamp.
MIL Lamp Flashes
Important: If the MIL lamp flashes on and off while driving the vehicle, the driver should find a safe place to park and stop the vehicle immediately. See figure for an example of the MIL lamp. The vehicle should be taken to an authorized Freightliner dealer as soon as possible for service. Continued driving with an illuminated MIL lamp could damage the emission system and void the warranty.
Fig. 1, MIL Lamp
The MIL lamp illuminates to indicate a fault that affects the emission system; a misfire condition is one example. Diagnosis and service may be required. To prevent serious damage to the vehicle, observe the following guidelines:
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Reduce vehicle speed.
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Avoid hard accelerations.
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Avoid steep uphill grades.
Once the MIL lamp begins flashing, the driver should find a safe place to stop. Turn the vehicle off, wait at least 10 seconds, and then restart the vehicle. If the MIL lamp continues to flash, observe the guidelines listed above and see a dealer for service as soon as possible.
MIL Lamp is on Constant (steady)
A constant (steady) MIL lamp indicates that an emission system malfunction has been detected on the vehicle. Diagnosis and service may be required. The following information may correct an emissions system malfunction.
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Make sure the fuel cap is fully installed. The diagnostic system can determine if the fuel cap has been left off or is incorrectly installed. A missing or loose fuel cap allows fuel to evaporate into the atmosphere. A few driving trips with the fuel cap properly installed should turn the MIL lamp off.
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If the vehicle has been driven through a deep puddle of water, the system could be wet. Inspect the electrical system and make sure it is not wet. This condition is usually corrected when the electrical system dries out. A few driving trips should turn the MIL lamp off.
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Make sure to fuel the vehicle with quality fuel. Poor fuel quality causes the engine not to run as efficiently as designed and can cause—
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stalling after start-up;
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stalling when the vehicle is changed into gear;
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misfiring;
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hesitation on acceleration; or
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stumbling on acceleration.
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If one or more of these conditions occur, change the fuel brand used. At least one full tank of the proper fuel will be required to turn the MIL lamp off. See 'Fuel' in this chapter for information on the proper fuel to use.
If the MIL lamp will not go off after performing the above steps, your dealer can check the vehicle. The dealer has the proper test equipment and diagnostic tools to fix any mechanical or electrical problems that may have developed.