Inspection Procedure 1

INSPECTION PROCEDURE 1: Communication with scan tool Is not possible. (Communication with ABS only Is not possible.)








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 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-02.

NOTE: After inspecting intermediate connector C-212, C-301, or C-303, inspect the wire. If intermediate connector C-212, C301, or C-303 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-02 damaged?
YES: Repair them and go to STEP 5.
NO: Go to Step 3.











STEP 3. Check the harness wire between ABS-ECU connector A-02 and data link connector C-26.

NOTE: After inspecting intermediate connector C-140 or C212, inspect the wire. If intermediate connector C-140 or C-212 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-02 and data link connector C-26 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-02 and ground.
Q: Are any harness wires between ABS-ECU connector A02 and ground damaged?
YES: Repair them and then go to STEP 5.
NO: 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.