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

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 23) 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 24) 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

DIAGNOSIS

Required Special Tool:
- MB991223: Harness Set





STEP 1. Check the power supply circuit at ABS-ECU connector A-85.
1. Disconnect connector A-85 and measure at the harness side.
2. Start the engine.
3. Measure the voltage between terminal 9 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-85

NOTE: After inspecting intermediate connectors C-17, C-11, D-08, and D-13, inspect the wire. If intermediate connector C-17, C-11, D-08, or D-13 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-85 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-85 and data link connector C-69.

NOTE: After inspecting intermediate connectors C-10 and C-17, inspect the wires. If intermediate connector C-10 or C-17 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-85 and data link connector C-69 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-86 and ground.
Q: Are any harness wires between ABS-ECU connector A86 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.