Toyota 3S-GE Repair Manual page 190

EG 176 ENGINE — EFI SYSTEM
DIAGNOSIS SYSTEM
DESCRIPTION
EG4IL—0l
The ECU contains a built—-in self—diagnosis system by which troubles with the engine signal
network are detected and the check engine warning light on the combination meter lights up.
By analyzing various signals as shown in the later table (See page EG—~182) the ECU detects
system malfunctions relating to the sensors or actuators.
The self—diagnosis system has 2 modes, a normal mode and a test mode.
If a malfunction is detected when in the normal mode, the ECU lights up the check engine warning
light to inform the driver of the occurrence of a malfunction. (For some codes the light does not
come on.) The light goes OFF automatically when the malfunction has been repaired. But the
diagnostic code(s) remains stored in the ECU memory. 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 check connector are connected. When 2 or more codes are
indicated, the lowest number (code) will appear first.
If a malfunction is detected when in the test mode, the ECU lights up the check engine warning
light to inform the technician of the occurrence of a malfunction (except for code Nos. 42, 43 and
51). In this case, TE2 and E1 terminals on the check connector should be connected as shown
later. (See page EG— 179).
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. 42, 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, as shown later. (See page EG—179)
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. This function fills up the self—diagnosis system. The test mode can
be implemented by the technician following the appropriate procedures of check terminal
connection and operation described later. (See page EG—179) M7 M
CHECK ENGINE WARNING LIGHT CHECK
1. The check engine warning light will come on when the
ignition switch is at ON and the engine is not running.
2. When the engine is started, the check engine warning
"CHECK" Engine Warning Light light should 9° Off-
lf the light remains on, the diagnosis system has
Pom, detected a malfunction or abnormality in the system.