If there is
any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis,
diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
Whenever ECU is replaced, ensure that the CAN bus lines are normal.
OPERATION
ABS-ECU contains the power supply circuit (+BM terminal) for the
pump motor. The pump motor is energised by the motor switch, which is incorporated in ABS-ECU.
The pump motor switch, which is incorporated in ABS-ECU, is always off unless the
motor solenoid valve check is activated when the vehicle is started.
ABS-ECU activates the pump motor by turning on the ECU built-in pump motor switch.
DIAGNOSIS CODE SET CONDITIONS
This diagnosis codes 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
When the power supply voltage of the pump motor, which is not in operation, is abnormally
high for a prolonged period
PROBABLE CAUSES
Current trouble
Fusible link malfunction
Damaged wiring harness and connectors
Abnormality in battery or alternator
ABS-ECU malfunction
Past trouble
Carry out diagnosis with particular emphasis on wiring harness and
connector failures between the power supply circuit (+BM terminal) to the ABS-ECU motor
and the earth circuit (GND1, GND2 terminal). For diagnosis procedures, refer to How to treat
past trouble (GROUP 00 - How to Use Troubleshooting/How to Treat Past Trouble ).
DIAGNOSTIC PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics
Use M.U.T.-III 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, go to Step 2.
STEP 2. Diagnosis code recheck after resetting CAN bus lines
Q.
Is the diagnosis code No.C2116 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 10.
STEP 4. Charging system check
Refer to GROUP 16 - On-vehicle Service/Alternator Output Line
Voltage Drop 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 10.
STEP 5. Fusible link check: Check the fusible link No.4 and SFB5.
Visually check for open circuit in the fusible link No.4 and SFB5.
Q.
Is the check result normal?
Go to Step 7.
Go to Step 6.
STEP 6. Resistance measurement at ABS-ECU connector
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Disconnect the fusible link No.4 or SFB5.
(3)Resistance between the +BM terminal and the body earth. OK: No continuity
Q.
Is the check result normal?
Replace the fusible link No.4 or SFB5. Then go to Step 10.
The short circuit may be present in the power supply circuit. Repair the wiring
harness between the ABS-ECU connector +BM terminal and the fusible link, and then replace
the fusible link No.4 or SFB5. Then go to Step 10.
STEP 7. Voltage measurement at the ABS-ECU connector
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Measure the voltage between the +BM terminal and the body earth. OK: Approximately system voltage
Q.
Is the check result normal?
Go to Step 8.
The open circuit may be present in the power supply circuit. Repair the wiring
harness between the ABS-ECU connector +BM terminal and the fusible link. Then go to
Step 10.
STEP 8. Resistance measurement at ABS-ECU connector
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Resistance between the GND1 terminal and the body earth, and between the GND2 terminal
and the body earth. OK: Continuity exists (2 Ω or less)
Q.
Is the check result normal?
Go to Step 9.
An open circuit may be present in the earth circuit. Repair the wiring harness
between the ABS-ECU connector GND1 terminal and the body earth, and between the ABS-ECU connector
GND2 terminal and the body earth. Then go to Step 10.
STEP 9. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note
The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h
or higher.
Q.
Is the diagnosis code No.C2116 set?
Replace the hydraulic unit (integrated with ABS-ECU) (Refer to ). Then
go to Step 10.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/ How
to Cope with Intermittent Malfunctions ).
STEP 10. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note
The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h
or higher.
Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table 
).
On completion, go to Step 2.