Description of On-Board Diagnostics

Input/Output Signal Of A/T Control Unit:

OPERATION
The A/T control unit receives signals sent from various switches and sensors. The control unit then determines required line pressure, shifting point, lock-up operation, engine brake operation. The unit sends required signals to the respective solenoids.

OBD-II
In accordance with the OBD-II requirements, A/T self-diagnoses have been improved as follows:
^ On the former models, the A/T control unit performed the self-diagnoses for A/T self-diagnostic items, and illuminated the power indicator lamp to indicate the self-diagnostic results. On the '94 model, the engine control module also receives the A/T self-diagnostic results and illuminates the malfunction indicator lamp (MIL) to indicate the results. The number of self-diagnostic items has increased. Increased items can not be indicated by the power indicator lamp.
^ The self-diagnostic results indicated by the MIL are automatically stored in the ECM and A/T control unit memories.

NOTE: The results stored in the memories (of both ECM and A/T control unit) must be erased each time after repairing the malfunctioning part.

^ The following can be used to display the self-diagnostic results indicated by the MIL and to erase the results stored in the ECM and A/T control unit memories.

ECM MEMORY
CONSULT (Select ENGINE)
Generic Scan Tool (GST)
Mode selector on ECM

A/T CONTROL UNIT MEMORY
CONSULT (Select A/T)
On-board self-diagnosis

^ As for the malfunctions indicated by the MIL, the relevant data (sensor signals, ECM signals, etc.) obtained at the' moment of detection can be verified by Freeze Frame Data.
^ All information on the A/T trouble diagnoses, including the self-diagnostic items indicated only by the MIL, is described in Automatic Transmission Control, Testing and Inspection.