1: Communication Between Scan Tool & ABS-ECU Is Not Possible

INSPECTION PROCEDURE 1: Communication between the Scan Tool and the ABS-ECU is not possible.





Part 1 of 2





Part 2 of 2

NOTE: CONNECTOR LOCK SWITCH
ON: The ABS-ECU connector A-02 is connected.
OFF: The ABS-ECU connector A-02 is disconnected.

CIRCUIT OPERATION
^ The diagnostic output is made from the ABS-ECU (terminal 11) to the diagnostic output terminal (terminal 7) of the data link connector.
^ When the data link connector's diagnostic test mode control terminal (terminal 1) is grounded, the ABS-ECU (terminal 12) 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-02.
1. Disconnect connector A-02 and measure at the harness side.
2. Start the engine.
3. Measure the voltage between terminal 15 and ground.
Q: Is voltage approximately 12 volt?
YES: Go to Step 3.
NO: Go to Step 2.











STEP 2. Check the harness wire between the ignition switch (IG2) and the ABS-ECU connector A-02.

NOTE: After inspecting the intermediate connectors C-94, C-111, and C-112, inspect the wire. If the intermediate connector C-94, C-111, or C-112 is damaged, repair or replace it. If the connector has been repaired or replaced, go to Step 5.

Q: Is the harness wire between the ignition switch (IG2) and the ABS-ECU connector A-02 damaged?
YES: Repair it and go to Step 5.
NO: Go to Step 3.














STEP 3. Check the harness wires between the ABS-ECU connector A-02 and the data link connector C-29.

NOTE: After inspecting the intermediate connectors C-77 and C-94, inspect the wires. If the intermediate connector C-77 or C-94 is damaged, repair or replace it. If the connector has been repaired or replaced, go to Step 5.

Q: Is any of the harness wires between the ABS-ECU connector A-02 and the data link connector C-29 damaged?
YES: Repair it and go to Step 5.
NO: Go to Step 4.





STEP 4. Check the harness wires between ABS-ECU connector A-02 and ground.
Q: Are any harness wires between ABS-ECU connector A-02 and ground damaged?
YES: Repair them and then go to Step 5.
NO: Go to Step 5.

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