Diagnostic Readout Box: Description and Operation

Controller Area Network (CAN):

PURPOSE
The diagnostic module (N59) monitors the engine control systems and their ECU's to assist the technician during the trouble shooting/checking process. If the module detects a system/component malfunction, it illuminates the "CHECK ENGINE" light in the instrument cluster.

DESIGN
The diagnostic module is equipped with a memory that retains malfunction codes even after the battery has been disconnected.

OPERATION
When the ignition is switched ON, engine control system data is transmitted, via the controller area network (CAN), to the diagnostic module and stored in the memory. The diagnostic module receives the necessary information from the following ECU's:
a. LH control unit (N3/1)
b. EZL/AKR control unit (N1/3)
c. Electronic accelerator control unit (N4/1)
d. ABS/ASR control unit (N30/1)

If a system malfunction occurs, the diagnostic module receives a malfunction code signal from the appropriate ECU. This code is stored in the module memory. If the same malfunction code occurs during two consecutive trips, the "CHECK ENGINE" light is illuminated and remains lit until the malfunction is eliminated.

The malfunction codes can be accessed via the diagnostic socket (X11/4) or push-button with LED (X11/21s1).