OBD-II Self Diagnosis

DESCRIPTION
The ECM (ECCS control module) provides two functions for the A/T system. One function is to receive a signal from the A/T control unit used with OBD-related parts of the A/T system. The signal is sent to the ECM when a malfunction occurs in the corresponding OBD-related part. The other function is to indicate a diagnostic result by means of the MIL (malfunction indicator lamp) on the instrument panel. Sensors, switches and solenoid valves are used as sensing elements.
The MIL automatically illuminates in One or Two Trip Detection Logic when a malfunction is sensed in relation to A/T system parts.

ONE TRIP DETECTION LOGIC
If a malfunction is sensed during the first test drive, the MIL will illuminate and the malfunction will be stored in the ECM memory as a DTC. The A/T control unit is not provided with such a memory function.

TWO TRIP DETECTION LOGIC
When a malfunction is sensed during the first test drive, it is stored in the ECM memory as a 1st trip DTC (diagnostic trouble code) or 1st trip freeze frame data. At this point, the MIL will not illuminate. - First Trip
If the same malfunction as that experienced during the first test drive is sensed during the second test drive, the MIL will illuminate. - Second Trip




A/T - related parts for which the MIL illuminates during the first or second test drive are listed in the image.
The "trip" in the "One or Two Trip Detection Logic" means a driving mode in which self-diagnosis is performed during vehicle operation.

OBD II SELF-DIAGNOSIS
A/T self-diagnosis is performed by the A/T control unit in combination with the ECM. The results can be read through the blinking pattern of the OD OFF indicator or the malfunction indicator lamp (MIL).

The self-diagnostic results indicated by the MIL are automatically stored in both the ECM and A/T control unit memories.
Always perform the procedure "HOW TO ERASE DTC" to complete the repair and avoid unnecessary blinking of the MIL.

The following self-diagnostic items can be detected using ECM self-diagnostic results mode* only when the OD OFF indicator lamp does not indicate any malfunctions.
1. Improper shifting to 1st, 2nd, 3rd, or 4th gear position.
2. Improper torque converter clutch operation.
3. Improper lock-up operation.