ASC

DTC C2116 Low power supply voltage in pump motor

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.
^ When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor.

OPERATION
^ ASC-ECU contains the power supply circuit (terminal No.1) for the pump motor. The pump motor is energized by the motor switch, which is incorporated in ASC-ECU.
^ The pump motor switch, which is incorporated in ASC-ECU, is always off unless the motor solenoid valve check is activated when the vehicle is started.
^ ASC-ECU activates the pump motor by turning on the ECU built-in pump motor switch.

DTC SET CONDITIONS
This DTCs will be set under the cases below:
^ When the power supply voltage of the pump motor, which is not in operation, is abnormally low for a prolonged period

PROBABLE CAUSES

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

Past trouble
^ Carry out diagnosis with particular emphasis on wiring harness and connector failures between the power supply circuit (A-51 ASC-ECU connector terminal No.1) to the ASC-ECU motor and the ground circuit (A-51 ASC-ECU connector terminal No.16 and 47). 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
^ MB991997: ASC check harness

STEP 1. M.U.T.-III CAN bus diagnosis
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 C2116 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-51 ASC-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 the fusible link No.26.
Visually check for open circuit in the fusible link No.26.

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

STEP 7. Resistance measurement at A-51 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 voltage at the special tool connector side.

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

2) Measure the voltage between the terminal No.1 and the body ground.
OK: Battery positive 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-51 ASC-ECU connector terminal No.1 and the fusible link No.26. Then go to Step 11.

STEP 9. Resistance measurement at A-51 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) Resistance between the terminal No.16 and the body ground, and between the terminal No.47 and the 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-51 ASC-ECU connector terminal No.16 and the body ground, and between the A-51 ASC-ECU connector terminal No.47 and the body ground. Then go to Step 11.

STEP 10. Check whether the DTC is reset.
1) Erase the DTC.
2) Drive the vehicle at 12 mph (20 km/h) or more.

NOTE: The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12 mph (20 km/h) or higher.

Q: Is DTC C2116 set?
YES: Replace the hydraulic unit (ASC-ECU). Then go to Step 11.
NO: Intermittent malfunction.

STEP 11. Check whether the DTC is reset.
1) Erase the DTC.
2) Drive the vehicle at 12 mph (20 km/h) or more.

NOTE: The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12 mph (20 km/h) or higher.

Q: Is DTC C2116 set?
YES: Return to Step 1.
NO: The procedure is complete.