Inspection Procedure 1

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









CIRCUIT OPERATION
^ The DTC is set by the ABS-ECU (terminal 13) 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 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 ABS-ECU connector B-118.





1. Disconnect ABS-ECU connector B-118 and measure at the harness side.
2. Start the engine.
3. Measure the voltage between terminal 20 and ground.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 3.
NO: Go to Step 2.

STEP 2. Check the harness wire between the ignition switch (IG2) connector C-208 terminal 4 and ABS-ECU connector B-118 terminal 20.








NOTE: After inspecting the intermediate connector C-122, C-210, and C-211, inspect the wire. If the intermediate connector C-122, C-210 or C-211 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) connector C-208 terminal 4 and ABS-ECU connector B-118 terminal 20 damaged?
YES: Repair it and go to Step 5.
NO: Go to Step 3.

STEP 3. Check the harness wires between ABS-ECU connector B-118 terminal 13 and data link connector C-14 terminal 7 or ABS-ECU connector B-118 terminal 4 and data link connector C-14 terminal 1.








NOTE: After inspecting intermediate connectors C-101, C-105, C-122 and C-124, inspect the wires. If the intermediate connector C-101, C-105, C-122 or C-124 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 ABS-ECU connector B-118 terminal 13 and data link connector C-14 terminal 7 or ABS-ECU connector B-118 terminal 4 and data link connector C-14 terminal 1 damaged?
YES: Repair it and go to Step 5.
NO: Go to Step 4.

STEP 4. Check the harness wires between ABS-ECU connector B-118 terminal 2 and ground or ABS-ECU connector B-118 terminal 18 and ground.








Q: Is any of the harness wires between ABS-ECU connector B-118 terminal 2 and ground or ABS-ECU connector B-118 terminal 18 and ground damaged?
YES: Repair it and then go to Step 5.
NO: Retest the system. If the malfunction persists, replace the hydraulic unit (integrated with ABS-ECU).Then go to Step 5. If the malfunction is not reproduced, then a transient malfunction is suspected. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.

STEP 5. Retest the system.
Q: Does the scan tool communicate with the ABS system?
YES: The procedure is complete.
NO: Return to Step 1.