1: Communication W/ Scan Tool Is Not Possible

SYMPTOM PROCEDURES

INSPECTION PROCEDURE 1: Communication With Scan Tool is not Possible. (Communication With ABS Only is not Possible.)





Part 1 of 2





Part 2 of 2

CIRCUIT OPERATION
^ The diagnostic output is made from the ABS-ECU (terminal 7) to the diagnostic output terminal (terminal 7) of the data link connector.
^ When the data link connectors diagnostic test mode control terminal (terminal 1) is grounded, the ABS-ECU (terminal 14) will go into diagnostic mode.

TECHNICAL DESCRIPTION (COMMENT)
When communication with the scan tool is not possible, the cause is probably an open circuit in the ABS-ECU power circuit or an open circuit in the diagnostic output circuit.

TROUBLESHOOTING HINTS (The most likely causes for this case:)
^ Blown fuse
^ Damaged wiring harness and connector
^ Malfunction of the hydraulic unit (Integrated with ABS-ECU)

DIAGNOSIS

Required Special Tool:
^ MB991223: Harness Set





STEP 1. Check the power supply circuit at ABS-ECU connector A-03.
1. Disconnect connector A-03 and measure at the harness side.
2. Start the engine.
3. Measure the voltage between terminal 4 and ground.
Q: Is voltage approximately 12 volts?
YES: Go to Step 3.
NO: Go to Step 2.











STEP 2. Check the harness wire between ignition switch (IG2) and ABS-ECU connector A-03.

NOTE: After inspecting intermediate connectors C-12, C-84, and C-87, inspect the wire. If intermediate connector C-12, C-84, or C-87 is damaged, repair or replace it. If the connector has been repaired or replaced, go to Step 3.

Q: Is any harness wire between ignition switch (IG2) and ABS-ECU connector A-03 damaged?
YES: Repair them and go to Step 5.
NO: Go to Step 5.














STEP 3. Check the harness wire between ABS-ECU connector A-03 and data link connector C-23.

NOTE: After inspecting intermediate connectors C-12 and C-57, inspect the wires. If intermediate connector C-12 or C-57 is damaged, repair or replace it. If the connector has been repaired or replaced, go to Step 4.

Q: Is any harness wire between ABS-ECU connector A-03 and data link connector C-23 damaged?
YES: Repair them and go to Step 5.
NO: Go to Step 4.





STEP 4. Check the harness wires between ABS-ECU connector A-03 and ground.
Q: Are any harness wires between ABS-ECU connector A-03 and ground damaged?
YES: Repair them and then go to Step 5.
NO: Replace the ABS-ECU and then go to Step 5.

STEP 5. Check symptoms.
Q: Does the scan tool communicate with the ABS system?
YES: This diagnosis is complete.
NO: Return to Step 1.