Inspection Procedure 1

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

Part 1 Of 2:

Part 2 Of 2:

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 switch to the 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 or 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 the ABS-ECU connector A-02.
1. Disconnect the ABS-ECU connector A-02 and measure at the harness side.
2. Start the engine.





3. Measure the voltage between terminal 15 and ground.
Q: Is the voltage approximately 12 volts (battery positive voltage)?
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 (terminal 15).








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 (terminal 15) 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 (terminals 11 and 12) and the data link connector C-29 (terminals 1 and 7).








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 (terminals 11 and 12) and the data link connector C-29 (terminals 1 and 7) damaged?
YES: Repair it and go to Step 5.
NO: Go to Step 4.

STEP 4. Check the harness wires between the ABS-ECU connector A-02 (terminals 16,19, and 30) and ground.





Q: Is any of the harness wires between the ABS-ECU connector A-02 (terminals 16, 19, and 30) and ground damaged?
YES: Repair it and then go to Step 5.
NO: Replace the hydraulic unit (integrated with ABS-ECU) and then go to Step 5.

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