Reading and Clearing Diagnostic Trouble Codes

ON BOARD DIAGNOSTIC (OBD) SYSTEM


Diagnosis Description

The A/T system has two self-diagnostic systems.
The first is the emission-related on board diagnostic system (OBD) performed by the TCM in combination with the ECM. A malfunction is indicated by the MI (malfunction indicator) and is stored as a DTC in the ECM memory and in the TCM memory.
The second is the TCM original self-diagnosis indicated by the TCM. A malfunction history is stored in the
TCM memory. The detected items are overlapped with OBD self-diagnostic items. For details, Testing and Inspection.

OBD FUNCTION
The ECM provides emission-related on board diagnostic (OBD) functions for the A/T system.
One function is to receive a signal from the TCM 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 MI (malfunction indicator) on the instrument panel. Sensors, switches and solenoid valves are used as sensing elements.
The MI automatically illuminates in "One or Two Trip Detection Logic" when a malfunction is sensed in relation to A/T system parts. For details, Diagnosis Description.