Active Stability Control System (ASC)

DTC C1608: Implausible diagnosis data

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 Initial Inspection and Diagnostic Overview ).
- Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
- When the hydraulic unit (integrated with ASC-ECU) is replaced, after turning the ignition switch ON and OFF (vehicle information from ETACS-ECU is registered), always perform the calibration of steering wheel sensor, G and yaw rate sensor, brake fluid pressure sensor, cut valve, and inlet valve (Refer to G and Yaw Rate Sensor Calibration , Testing and Inspection , Master Cylinder Brake Fluid Pressure Sensor Calibration , and Testing and Inspection ).
- When the ASC-ECU connector or battery terminal is disconnected with the ignition switch ON, this diagnostic trouble code may be set.
- When this diagnostic trouble code is set, no other failure information will be set.

CIRCUIT OPERATION

- The ASC-ECU stores diagnostic trouble codes and failure information in the EEPROM*.
- ASC-ECU (EEPROM*) contains the power supply circuit (terminal No.2).

NOTE:
*:EEPROM (Electrical Erasable and Programmable ROM)

DTC SET CONDITIONS

This diagnostic trouble code is set under the cases below.

- Trouble information stored in the EEPROM is not reliable.
- ASC-ECU power supply is shut down while the trouble information is being written to EEPROM.

PROBABLE CAUSES

- Disconnection of the ASC-ECU connector or the battery terminal when the ignition switch is ON
- Loose battery terminal
- Abnormality in battery
- Damaged wiring harness and connectors
- ASC-ECU malfunction

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?

YES Go to Step 3.
NO Repair the CAN bus lines. CAN Bus Diagnostics Chart.) After repairing the CAN bus line, go to Step 2.
STEP 2. DTC recheck after repairing the CAN bus line

Q. Is DTC C1608 set?

YES Go to Step 3.
NO This diagnosis is complete.
STEP 3. Battery check

Battery Test.

Q. Is the battery in good condition?

YES Go to Step 5.
NO Go to Step 4.
STEP 4. Charging system check

Output Current Test.

Q. Is the charging system in good condition?

YES Replace the battery. Then go to Step 15.
NO Repair or replace the charging system component(s), and then go to Step 15.
STEP 5. Connector check: A-05 ASC-ECU connector, C-131 intermediate connector, C-309 ETACS-ECU connector, C-315 ETACS-ECU connector

Q. Is the check result normal?

YES Go to Step 6.
NO : Repair the defective connector, and then go to Step 15.
STEP 6. Check of fusible link No. 27

Visually check for open circuit in the 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-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: Approximately system voltage

Q. Is the check result normal?

YES Go to Step 9.

NO An open circuit may be present in the power supply circuit. Repair the wiring harness between A-05 ASC-ECU connector terminal No.32 and the fusible link No.27, and then go to Step 15.

STEP 9. Check of fusible link No.34

Visually check for open circuit in the fusible link No.34.

Q. Is the check result normal?

YES Go to Step 11.
NO Go to Step 10.
STEP 10. Resistance measurement at C-309 ETACS-ECU connector

(1)Disconnect the connector, and measure the resistance at the harness connector side.

(2)Measure the resistance between the terminal No.1 and the body ground.
OK: No continuity

Q. Is the check result normal?

YES Replace the fusible link No.34, and then go to Step 15.
NO An short circuit may be present in the power supply circuit. Repair the wiring harness between C-309 ETACS-ECU connector terminal No.1 and the fusible link No.34. Replace the fusible link No.34, and then go to Step 15.
STEP 11. Check of fuse No.17

Visually check for open circuit in the fuse No.17.

Q. Is the check result normal?

YES Go to Step 13.
NO Go to Step 12.
STEP 12. 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, and between the terminal No.47 and the body ground
OK: Continuity exists (2ohms or less)

Q. Is the check result normal?

YES Go to Step 15.

NO An open circuit may be present in the ground circuit. Repair the wiring harness between A-05 ASC-ECU connector terminal No. 16 and the body ground as well as between A-05 ASC-ECU connector terminal No. 47 and the body ground, and then go to Step 15.

STEP 15. Check whether the DTC is reset.

(1)Erase the diagnostic trouble code.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Turn the ignition switch to the "ON" position.

(4)Perform a test run of the vehicle at the vehicle speed of 12 mph (20 km/h) or more. Then, check if the diagnostic trouble code is set in ASC-ECU.

Q. Is the DTC set?

YES (DTC C1608 is set) : Replace the hydraulic unit (integrated with ASC-ECU) (Refer to Service and Repair).
YES (DTC other than C1608 is set) : Carry out the applicable troubleshooting for the DTC.
NO This diagnosis is complete.