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.)

Data Link Connector Circuit





Part 1 of 2





Part 2 of 2

CIRCUIT OPERATION
- The diagnostic output is made from the ABS-ECU (terminal 7) 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 14) 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 circus 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-03.
1. Disconnect connector A-03 and measure at the harness side.
2. Start the engine.
3. Measure the voltage between terminal 4 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-03

NOTE: After inspecting intermediate connect or C-12, C-73, or C-77, inspect the wire. If intermediate connector C-12, C-73, or G77 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-03 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-03 and data fink connector C-23.

NOTE: After inspecting intermediate connector C- 12 or C-57, inspect the wire. If intermediate connector C-12 or C-57 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-03 and data link connector C-23 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-03 and ground.
Q: Are any harness wires between ABS-ECU connector A-03 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.