DTC C2104: Faulty valve power supply circuit

caution

If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines.
Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
When the hydraulic unit (integrated with ASC-ECU) is replaced, always perform the calibration of steering wheel sensor, G and yaw rate sensor, brake fluid pressure sensor, cut valve, and inlet valve.(Refer to , , , and .)

CIRCUIT OPERATION

ASC-ECU contains the power supply circuit (terminal No. 32) for the solenoid valve. The solenoid valve is energized by the valve relay, which is incorporated in ASC-ECU.
The valve relay in ASC-ECU is energized at all times, and the solenoid valve is always energized while the system is in operation unless the initial check is in progress when the ignition switch is turned ON, or unless the periodical system check is in progress.

DTC SET CONDITIONS

This diagnostic trouble code is set when the solenoid valve supply voltage is out of the standard value.

PROBABLE CAUSES

Current trouble

Fusible link malfunction
Damaged wiring harness and connectors
Abnormality in battery or generator
ASC-ECU malfunction

Past trouble

Carry out the diagnosis with a particular emphasis on the wiring harness and connector failures in the ASC-ECU solenoid valve power supply circuit (terminal No. 32) and in the ground circuit (terminal No. 16 and No. 47). For diagnosis procedures, refer to How to Treat Past Trouble (GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).

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

MB991997: ASC check harness

STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.

Using scan tool MB991958, diagnose the CAN bus lines.

Q. Is the check result normal?

	Go to Step 3.

	Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics table ). On completion, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line

Q. Is DTC C2104 set?

	Go to Step 3.

	This diagnosis is complete.

STEP 3. Battery check

Refer to GROUP 54A - Battery Test

Q. Is the battery in good condition?

	Go to Step 4.

	Replace the battery. Then go to Step 11.

STEP 4. Charging system check

Refer to GROUP 16 - Output Current Test

Q. Is the charging system in good condition?

	Go to Step 5.

	Repair or replace the charging system component(s). Then go to Step 11.

STEP 5. Connector check: A-05 ASC-ECU connector

Q. Is the check result normal?

	Go to Step 6.

	NO : Repair the defective connector. Then go to Step 11.

STEP 6. Fusible link check: Check the fusible link No.27.

Visually check for open circuit in the fusible link No.27.

Q. Is the check result normal?

	Go to Step 8.

	Go to Step 7.

STEP 7. Resistance measurement at A-05 ASC-ECU connector

(1)Disconnect the ASC-ECU connector, connect special tool ASC check harness (MB991997) to the harness-side connector, and then measure the resistance at the special tool connector side.

note

Do not connect the special tool ASC check harness (MB991997) to ASC-ECU.

(2)Disconnect the fusible link No.27.
(3)Resistance between the terminal No.32 and the body ground.
OK: No continuity

Q. Is the check result normal?

Replace the fusible link No.27. Then go to Step 11.

The short circuit may be present in the power supply circuit. Repair the wiring harness between the A-05 ASC-ECU connector terminal No.32 and the fusible link No.27, and then replace the fusible link No.27. Then go to Step 11.

STEP 8. Voltage measurement at A-05 ASC-ECU connector

(1)Disconnect the connector, connect the special tool ASC check harness (MB991997) to the wiring harness-side connector, and measure the voltage at the special tool connector side.

note

Do not connect the special tool to ASC-ECU.

(2)Measure the voltage between the terminal No. 32 and the body ground.
OK: Battery positive voltage

Q. Is the check result normal?

Go to Step 9.

The open circuit may be present in the power supply circuit. Repair the wiring harness between the A-05 ASC-ECU connector terminal No.32 and the fusible link No.27. Then go to Step 11.

STEP 9. Resistance measurement at A-05 ASC-ECU connector

(1)Disconnect the connector, connect the special tool ASC check harness (MB991997) to the wiring harness-side connector, and measure the voltage at the special tool connector side.

note

Do not connect the special tool to ASC-ECU.

(2)Measure the resistance between the terminal No. 16 and the body ground as well as between the terminal No. 47 and the body ground.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Go to Step 10.

An open circuit may be present in the ground circuit. Repair the wiring harness between the A-05 ASC-ECU connector terminal No.16 and the body ground, and between the A-05 ASC-ECU connector terminal No.47 and the body ground. Then go to Step 11.

STEP 10. Check whether the DTC is reset.

Q. Is DTC C2104 set?

	Replace the hydraulic unit (incorporates in ASC-ECU).(Refer to .) Then go to Step 11.

	Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)

STEP 11. Check whether the DTC is reset.

Q. Is DTC C2104 set?

	Return to Step 1.

	This diagnosis is complete.