Inspection Procedure 1: M.U.T.-III cannot communicate only with ABS-ECU.


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caution If the battery voltage increases abnormally, the ABS-ECU is deactivated, and then the ABS warning lamp is illuminated, disabling the communication with M.U.T.-III. For proper troubleshooting, check the status of battery, alternator, etc. before the following inspections. Then repair or replace if necessary.

OPERATION


The ABS-ECU and diagnosis connector are connected between the following terminals, and the ABS-ECU communicates with the M.U.T.-III using this communication lines.

COMMENT ON TROUBLE SYMPTOM


When the M.U.T-III and the ABS-ECU cannot communicate, the following situations are suspected.

PROBABLE CAUSES


The most likely causes for this case are:

DIAGNOSIS

STEP 1. Inspect the open or short of communication line between the ABS-ECU connector D-250 and the diagnosis connector D-127.
note Prior to the wiring harness inspection, check the junction connector D-34 and the intermediate connector D-230, and repair if necessary.
Check the following wiring harnesses.

  • ABS-ECU connector D-250 terminal No.36 - diagnosis connector D-127 terminal No.7
  • ABS-ECU connector D-250 terminal No.47 - diagnosis connector D-127 terminal No.1

Q. Is the check result normal?
Go to Step 2.
Repair the wiring harness between the ABS-ECU connector D-250 and the diagnosis connector D-127.

STEP 2. Inspect the open circuit between the ABS-ECU connector D-250 and D-251 and the earth.
Disconnect the ABS-ECU connector D-250 and D-251, and measure the continuity between the body earth and the following terminals at the harness-side connector.

  • ABS-ECU connector D-251 terminal No.12 - earth
  • ABS-ECU connector D-251 terminal No.25 - earth
  • ABS-ECU connector D-251 terminal No.26 - earth
  • ABS-ECU connector D-250 terminal No.42 - earth
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?
Go to Step 3.
Repair the wiring harness between the ABS-ECU connector D-250 and D-251 and the earth.

STEP 3. Inspect the open and short circuit in the power source line to the ABS-ECU connector D-250 and D-251.
note Prior to the wiring harness inspection, check the intermediate connector D-217 and D-222, the joint connector D-14 and D-132, and the junction block connector D-403 and D-405. Then repair if necessary.
Check the wiring harnesses between the following terminals.

  • Ignition switch (IG2) connector D-309 terminal No. 4 - ABS-ECU connector D-251 terminal No. 31
  • Ignition switch (IG2) connector D-309 terminal No. 4 - ABS-ECU connector D-251 terminal No. 13

Q. Is the check result normal?
Go to Step 4.
Repair the wiring harness between the ignition switch (IG2) connector D-309 terminal No.4 and ABS-ECU connector D-251 terminal No.31 or between ignition switch (IG2) connector D-309 terminal No.4 and ABS-ECU connector D-251 terminal No.13.

STEP 4. Retest the system.

Q. Can the M.U.T-III communicate with the ABS-ECU?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .
Replace the ABS-ECU.