Anti-Lock Braking System (ABS)

DTC C1608: Implausible diagnosis data









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 ).
- If the ABS-ECU connector is disconnected or the battery terminal is disconnected when the ignition switch is ON, this DTC may be set.
- Since the failure information stored in the past is erased after this diagnosis is carried out, reproduce the state of malfunction.

CIRCUIT OPERATION

The ABS-ECU stores DTCs and failure information in the EEPROM*.

The ABS-ECU is energized by the solenoid valve power supply circuit (terminal No.26).

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

DTC SET CONDITIONS

- This DTC is set when the failure information stored in the EEPROM is not reliable. The failure information stored in the past is not output, and only this DTC is set.
- This DTC may occur when ABS-ECU power supply shutdown or drop between ABS-ECU is writing a data to the EEPROM.

PROBABLE CAUSES

- Disconnection of the ABS-ECU connector or the battery terminal when the ignition switch is ON
- Loose battery terminal
- Abnormality in battery
- Damaged wiring harness and connectors
- ABS-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
- 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, and then go to Step 2.
STEP 2. DTC recheck after resetting CAN bus lines

Q. Is DTC C1608 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 5.
NO Go to Step 4.
STEP 4. Charging system check

Generator Output Line Voltage Drop Test.

Q. Is the charging system in good condition?

YES Replace the battery. Then go to Step 9.
NO Repair or replace the charging system component(s).
STEP 5. Voltage measurement at the A-03 ABS-ECU connector





(1)Disconnect the 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 terminal No.26 and body ground.
OK: Battery positive voltage

Q. Is the check result normal?

YES Go to Step 7.

NO Go to Step 6.

STEP 6. Connector check: A-03 ABS-ECU connector

Q. Is the check result normal?

YES The open or 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 fusible link No.27.
NO : Repair the defective connector.
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)Measure the resistance between terminal No.1 and body ground, and between terminal No.14 and body ground.
OK: Continuity exists (2ohms or less)

Q. Is the check result normal?

YES Go to Step 9.

NO Go to Step 8.

STEP 8. Connector check: A-03 ABS-ECU connector

Q. Is the check result normal?

YES An open circuit may be present in the ground circuit. Repair the wiring harness between the A-03 ABS-ECU terminal No.1 and body ground, and between the A-03 ABS-ECU terminal No.14 and body ground.
NO : Repair the defective connector.
STEP 9. Check whether the DTC is reset.

(1)Erase the DTC.

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

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

Q. Is DTC C1608 set?

YES Replace the hydraulic unit (integrated with ABS-ECU) (Refer to Anti-Lock Braking System (ABS)).
Then go to Step 10.
NO Go to Step 11.
STEP 10. Check whether the DTC is reset.

Drive the vehicle at 20 km/h or more.

Q. Is DTC C1608 set?

YES Return to Step 1.
NO Go to Step 11.
STEP 11. Check the other DTCs.

Drive the vehicle at 12mph (20 km/h) or higher.

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

Q. Is any DTC set?

YES Carry out the applicable troubleshooting for the DTC (Refer to Anti-Lock Braking System (ABS)).
NO The procedure is complete.