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 (Refer to GROUP 54C, Trouble code diagnosis ).
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^*.

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. M.U.T.-III CAN bus diagnostics

Use scan tool to 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, and then go to Step 2.

STEP 2. DTC recheck after resetting CAN bus lines

Q. Is DTC C1608 set?

	Go to Step 3.

	The procedure is complete.

STEP 3. Battery check

Refer to GROUP 54A - Battery Test

Q. Is the battery in good condition?

	Go to Step 5.

	Go to Step 4.

STEP 4. Charging system check

Refer to GROUP 16 - Output Current Test

Q. Is the charging system in good condition?

	Replace the battery. Then go to Step 9.

	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?

Go to Step 7.

Go to Step 6.

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

Q. Is the check result normal?

	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)Resistance between terminal No.1 and body ground, and between terminal No.14 and body ground.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Go to Step 9.

Go to Step 8.

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

Q. Is the check result normal?

	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 any DTC set?

	YES (DTC C1608 is set) : Replace the hydraulic unit (ABS-ECU) (Refer to ).

	YES (DTC other than C1608 is set) : Carry out the applicable troubleshooting for the DTC.

	The procedure is complete.