The ECM contains a built-in, self-diagnosis system which detects troubles within the engine signal network. Once a malfunction is detected, the Malfunction Indicator Lamp (MIL), located on the instrument panel, will light.
By analyzing various signals, the ECM detects system malfunctions related to the operating sensors. The ECM stores the failure code associated with the detected failure until the diagnosis system is cleared.
The MIL on the instrument panel informs the driver that a malfunction has been detected. The light will go out automatically once the malfunction has been cleared.
It will need to go to the shop for this diagnoses.
DATA LINK CONNECTOR (DLC)
See Figures 1, 2 and 3
The DLC1 is located in the engine compartment. The DLC3 is located in the interior of the vehicle, under the driver's side dash.
Fig. 1: The Data Link connector (DLC1) is in the engine compartment and clearly labeled
Fig. 2: The Data Link connector (DLC) has several terminals inside for testing purposes
Fig. 3: The DLC3 is located under the dash
If you have further questions on this, please feel free to reply.
Thanks for asking!