Anti-Lock Braking System (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 CAN Bus Diagnostics Chart).

- 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
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. Using scan tool MB991958, diagnose the CAN bus lines.

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 CAN Bus Diagnostics Chart).
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

Battery Test.

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

Generator Output Line Voltage Drop Test.

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: 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 ground circuit. Repair the wiring harness between the A-03 ABS-ECU connector terminal No.1 and the body ground, and between the A-03 ABS-ECU connector terminal No.14 and the body ground. Then go to Step 11.

STEP 10. Check whether the DTC is reset.

Q. Is DTC C2104 set?

YES Replace the hydraulic unit (integrated with ABS-ECU) (Refer to Anti-Lock Braking System (ABS)). Then go to Step 11.
NO Intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 11. Check whether the DTC is reset.

Q. Is DTC C2104 set?

YES Return to Step 1.
NO The procedure is complete.