ABS

DTC C2104: Malfunction of power supply circuit





CAUTION
^ If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines.
^ Whenever ECU is replaced, ensure that the CAN bus lines are normal.

CIRCUIT OPERATION
^ ABS-ECU contains the power supply circuit (terminal No.26) for the solenoid valve. The solenoid valve is energized by the valve relay, which is incorporated in ABS-ECU.
^ The valve relay, which is incorporated in ABS-ECU, is always energizing the solenoid valve unless the initial check is in progress when the ignition switch is turned on, or the recurrent system check is in progress.

DTC SET CONDITIONS
This DTC will be set when the solenoid valve supply voltage is not within the standard value.

PROBABLE CAUSES

Current trouble
^ Fusible link malfunction
^ Damaged wiring harness and connectors
^ Abnormality in battery or generator
^ ABS-ECU malfunction

Past trouble
^ Carry out diagnosis with particular emphasis on wiring harness and connector failures between the power supply circuit (terminal No.26) to ABS-ECU solenoid valve or ground circuit (terminal No.14). For diagnosis procedures, refer to How to treat past trouble.

DIAGNOSIS

Required Special Tools:
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A
^ MB991974: ABS check harness

STEP 1. M.U.T.-III CAN bus diagnostics
Use scan tool to diagnose the CAN bus lines.

Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. On completion, go to Step 2.

STEP 2. DTC recheck after resetting CAN bus lines

Q: Is DTC C2104 set?
YES: Go to Step 3.
NO: The procedure is complete.

STEP 3. Battery check

Q: Is the battery in good condition?
YES: Go to Step 4.
NO: Replace the battery. Then go to Step 11.

STEP 4. Charging system check

Q: Is the charging system in good condition?
YES: Go to Step 5.
NO: Repair or replace the charging system component(s). Then go to Step 11.

STEP 5. Connector check: A-03 ABS-ECU connector

Q: Is the check result normal?
YES: Go to Step 6.
NO: Repair the defective connector. Then go to Step 11.

STEP 6. Fusible link check: Check fusible link No.27.
Visually check for open circuit in fusible link No.27.

Q: Is the check result normal?
YES: Go to Step 8.
NO: Go to Step 7.

STEP 7. Resistance measurement at A-03 ABS-ECU connector





1) Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the harness-side connector, and then measure the resistance at the special tool connector side.

NOTE: Do not connect the special tool to ABS-ECU.

2) Disconnect the fusible link No.27.
3) Measure the resistance between the terminal No.26 and the body ground.
OK: No continuity

Q: Is the check result normal?
YES: Replace the fusible link No.27. Then go to Step 11.
NO: The short circuit may be present in the power supply circuit. Repair the wiring harness between the A-03 ABS-ECU connector terminal No.26 and the fusible link No.27, and then replace the fusible link No.27. Then go to Step 11.

STEP 8. Voltage measurement at the A-03 ABS-ECU connector





1) Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the harness-side connector, and measure the voltage at the special tool connector side.

NOTE: Do not connect the special tool to ABS-ECU.

2) Measure the voltage between the terminal No.26 and body ground.
OK: Approximately battery voltage

Q: Is the check result normal?
YES: Go to Step 9.
NO: The open circuit may be present in the power supply circuit. Repair the wiring harness between the A-03 ABS-ECU connector terminal No.26 and the fusible link No.27. Then go to Step 11.

STEP 9. Resistance measurement at A-03 ABS-ECU connector





1) Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the harness-side connector, and measure the resistance at the special tool connector side.

NOTE: Do not connect the special tool to ABS-ECU.

2) Measure the resistance between the terminal No.1 and body ground, and between terminal No.14 and body ground.
OK: Continuity exists (2 Ohms or less)

Q: Is the check result normal?
YES: Go to Step 10.
NO: An open circuit may be present in the earth circuit. Repair the wiring harness between the A-03 ABS-ECU connector terminal No.1 and the body earth, and between the A-03 ABS-ECU connector terminal No.14 and the body earth. Then go to Step 11.

STEP 10. Check whether the DTC is reset.

Q: Is DTC C2104 set?
YES: Replace the hydraulic unit (ABS-ECU). Then go to Step 11.
NO: Intermittent malfunction.

STEP 11. Check whether the DTC is reset.

Q: Is DTC C2104 set?
YES: Return to Step 1.
NO: The procedure is complete.