1: Communication W/Scan Tool Is Not Possible (ABS)

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

Data Link Connector Circuit





Part 1 of 3





Part 2 of 3





Part 3 of 3

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 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.

NOTE: After inspecting the intermediate connector C-94, C-101, or C-107, inspect the wire. If the intermediate connector C-94, C-101, or C-107 is damaged, repair or replace it. If the connector has been repaired or replaced, go to Step 3.

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 connector C-77 or 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 4.

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 me ABS-ECU connector A-02 and ground.
Q: Is any of the harness wires between the ABS-ECU connector A-02 and ground damaged?
YES: Repair it 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.