Self-Diagnosis System

Fig. 3 Speed Control Self-Diagnosis Description & Display Chart:

The self-diagnosis function senses a malfunction of the automatic speed control system (ASC) not made by the driver. To diagnose which circuit or what operation caused the malfunction of the ASC system, connect a suitable voltmeter and a multi-use tester to the diagnosis harness connector. The display of the malfunction data starts, if vehicle speed decreases to less than approximately 12 mph after the malfunction of ASC system, and stops if the vehicle speed increases to approximately 12 mph or higher, Fig. 3.
The ASC system performs control functions for setting or cancellation of vehicle fixed speed based on data provided by input signals. When the ASC system is canceled, the cause is stored in ECU memory in the form of a diagnosis code. If the ECU power supply is turned off, the diagnosis codes will be erased. The vehicle power supply must remain on until system diagnosis is complete.