Diagnosis System

Check Engine Light:

System Overview
The ECU contains a built-in self diagnosis system by which troubles with the engine signal network are detected and a "CHECK" engine warning light on the instrument panel lights up.

By analyzing various signals, the Electronic Control Unit (ECU) detects system malfunctions relating to the sensors or actuators.

A test mode function has been added to the functions of the self-diagnosis system of the normal mode for the purpose of detecting malfunctions such as poor contact, which are difficult to detect in the normal mode. The test mode can be implemented by the technician following the appropriate procedures of checking terminal connection and operations.

Diagnostic Connectors - Normal Mode:

Normal Mode
In the normal mode, the self-diagnosis system monitors 21 Items, indicated by code number. A "CHECK" engine warning light informs the driver that a malfunction has been detected. The light goes off automatically when the malfunction has been repaired. But the diagnostic code(s) remains stored in the ECU memory (except for code Nos. 16 and 53). The ECU stores the code(s) until it is cleared by removing the EFI fuse with the ignition switch off.

The diagnostic code can be read by the number of blinks of the "CHECK" engine warning light when TE1 and E1 terminals on the TDCL or check connector are connected. When 2 or more codes are indicated, the lowest number (code) will appear first.

Installing Jumper - Test Mode:

Test Mode
In the test mode, 17 items, indicated by code number, are monitored. If a malfunction is detected in any one of the systems indicated by code Nos. 13, 21, 22, 24, 25, 26, 27, 28, 29, 35, 41, 47 and 71 the ECU lights the "CHECK" engine warning light to warn the technician that malfunction has been detected. In this case, TE2 and E1 terminals on the TDCL should be connected as shown later.

Reading Codes In Test Mode:

In the test mode, even if the malfunction is corrected, the malfunction code is stored in the ECU memory even when the ignition switch is off (except code Nos. 17, 18,43 and 51). This also applies in the normal mode. The diagnostic mode (normal or test) and the output of the "CHECK" engine warning light can be selected by connecting the TE1, TE2 and E1 terminals on the check connector or TDCL1 as shown.