Description of On-Board Diagnostics

DESCRIPTION







1. A self-diagnosis function is built into the electrical control system. Warning is indicated by the overdrive OFF indicator.

HINT: Warning and diagnostic codes can be read only when the overdrive switch is ON. If OFF, the overdrive OFF indicator is lit continuously and will not blink.

a. If a malfunction occurs within the speed sensors or solenoids, the overdrive OFF light will blink to warn the driver.
However, there will be no warning of a malfunction with lock-up solenoid.

b. The diagnostic code can be read by the number of blinks of the overdrive OFF indicator when terminals T(T) and E(1) are short-circuited.
c. The throttle position sensor or brake signal are not indicated, but inspection can be made by checking the voltage at terminal T(T) of the check connector.
d. The signals to each gear can be checked by measuring the voltage at terminal T(T) of the check connector while driving.




2. The diagnostic (malfunction) code is retained in memory by the ECU and due to back-up voltage, is not canceled out when the engine is turned off. Consequently, after repair, it is necessary to turn the ignition switch off and remove the fuse EFI (15A) (A540E) or DOME (20A) (A540H) or disconnect the Engine and ECT ECU (A540E) or ECT ECU (A540H) connector to cancel out the diagnostic (malfunction) code.

HINT:
- Low battery voltage will cause faulty operation of the diagnosis system. Therefore, always check the battery first.
- Use a voltmeter and ohmmeter that have an impedance of at least 10 kOhms/V.