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Malfunction Indicator Lamp (MIL):
When the vehicle on board computer detects a problem in the emission related systems or components, its diagnostic program will assign a fault code (DTC) and store it in its memory. It also records a “Freeze Frame” of the conditions present when the fault was found and set the malfunction indicator lamp (MIL) alight. Some faults require detection
for two trips in a row before the MIL is turned on.
Three typical examples of MIL are shown below:
Definition of Trip
‘A Trip’ is define as a
module (PCM) detects the following: | o |
|
• Engine coolant temperature should exceed 70 C | o | |
•Engine coolant temperature should change more than 20 C after starting the engine.
•Engine speed should go over 400 RPM.
st
When the powertain control module (PCM) detects a fault during the 1 trip, the DTC and the corresponding ‘Freeze Frame’ data are stored in the PCM’snd memory. The MIL will not light up until the fault is again detected during the 2 trip. Certain DTCs are
capable of turning the MIL on or blinking during the first trip.