Initial Inspection and Diagnostic Overview

EXPLANATION ABOUT THE SCAN TOOL (M.U.T.-III) CAN BUS DIAGNOSTICS

Scan tool MB991958 CAN bus diagnostics carries out the two checks below automatically, and then displays current condition of the CAN bus lines according to the check results.

CAN BUS LINE DIAGNOSTIC FLOW





1. Scan tool CAN bus diagnostics
Scan tool MB991958 diagnoses CAN bus lines in accordance with the following strategy.
NOTE:
After you determine whether the CAN-C lines are in good condition, then determine whether the CAN-B lines are in good condition. Then confirm each judgment result on the scan tool screen.

(1) Check that the ETACS-ECU sets a diagnostic trouble code.
You can narrow down the points to be diagnosed by confirming an ETACS-ECU diagnostic trouble code.
(2) Checking the communication condition of ECUs
Scan tool MB991958 narrows down troubles in circuit by itself. Its strategies are as follows.










2. Pinpoint possible trouble spot according to diagnostic trouble code
If diagnostic trouble code related to CAN communication is set as past trouble, isolate opens as described below.
NOTE:
If you pinpoint trouble spot according to diagnostic trouble code, you should use time-out diagnostic trouble code. Diagnostic trouble code related to failure information is set when the data to be set contains an error, so CAN bus line itself is probably normal.

NOTE:
Time-out diagnostic trouble codes are stored in each ECU memory individually. Therefore, it is possible that these diagnostic trouble codes have not been set simultaneously. If the trouble spot cannot be found when you diagnose by judging from multiple diagnostic trouble codes, check the communication lines between each ECU.