California Vehicles

DIAGNOSIS SYSTEM DESCRIPTION

Diagnosis System Circuit:

Malfunction Indicator Lamp (MIL) Location:

The ECM contains a built-in self-diagnosis system by which troubles with the engine signal network are detected and a Malfunction Indicator Lamp (MIL) in the combination meter lights up.
By analyzing various signals the ECM detects system malfunctions relating to the sensors or actuators.
The self-diagnosis system has 2 modes, a Normal Mode and a Test Mode.

Normal Mode
If a malfunction is detected when in the Normal Mode, the ECM lights up the MIL to inform the driver of the occurrence of a malfunction. (NOTE: For some codes the MIL does not come on.) The MIL goes off automatically when the malfunction has been repaired, but the diagnostic trouble code(s) remains stored in the ECM memory (except for code No.16) until it is cleared by removing the EFI fuse for 10 seconds or more (depending on temperature) with the ignition switch OFF.
The diagnostic trouble code can be read by the number of blinks of the MIL when TE1 and E1 terminals of the DLC1 are connected.
When 2 or more codes are indicated, the lowest number (code) will appear first.

Test Mode
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.
Test Mode is implemented by connecting terminals TE2 and E1 of the DLC1 before turning the ignition switch ON.
If a malfunction is detected when in Test Mode, the ECM lights up the MIL to inform the technician of the occurrence of a malfunction (except for code Nos.42, 43 and 51).
In the Test Mode, even if the malfunction is corrected, the trouble code is stored in the ECM memory even when the ignition switch is OFF (except code Nos. 43 and 51).