If there is any problem in
the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, always diagnose
the CAN bus lines.
OPERATION
If 4WD-ECU determines that the vehicle is used under some severe operational conditions
(such as a long-time driving in 4WD on a sandy road, slushy road or road with deep snows or
towing or long hill-climbing), 4WD-ECU detects the overload to the coupling. If abnormal overload
is detected, 4WD-ECU interrupts the system to prevent it from being damaged.
DIAGNOSIS CODE SET CONDITIONS
If the following conditions are met, 4WD-ECU gradually switches the control from 4WD to
2WD, makes the drive system fluid temperature warning lamp illuminate, and sets the diagnosis
code No. C145F.
Drive mode-selector: 4WD or LOCK
When the load to the electronic control coupling is large, the mode is switched
to the 2WD mode.
PROBABLE CAUSES
Current trouble
The driving conditions are severe.
Electronic control coupling failure (clutch slippage)
4WD-ECU malfunction
Abnormality in ABS wheel speed signal
Abnormality in torque command value from the ABS/ASC-ECU
Past trouble
The past driving conditions were severe.
Electronic control coupling intermittent failure (clutch slippage)
Abnormality in ABS wheel speed signal
Abnormality in torque command value from the ABS/ASC-ECU
DIAGNOSIS 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 4.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting/CAN
Bus Diagnostics Table ). On completion, go to Step 2.
STEP 2. Check whether the diagnosis code is reset after repairing
the CAN bus line.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3)Check if the diagnosis code is set.
Q.
Is the diagnosis code No. C145F set?
Go to Step 3.
This diagnosis is complete.
STEP 3. M.U.T.-III data list
Check the following data list (Refer to ).
Item 07: CAN data (ABS/ASC)
Item 16: FL wheel speed sensor
Item 17: FR wheel speed sensor
Item 18: RL wheel speed sensor
Item 19: RR wheel speed sensor
Q.
Is the check result normal?
Go to Step 4.
Troubleshoot the ABS system (Refer to GROUP 35B - Troubleshooting/Diagnosis
Code Chart <Vehicles with ABS>), the ASC system (Refer
to GROUP 35C - Troubleshooting/Diagnosis Code Chart <Vehicles
with ASC>). Then go to Step 4.
STEP 4. M.U.T.-III actuator test
On a chassis dynamometer test, use M.U.T.-III to forcibly activate the electronic control
coupling from 600 N·m to 730 N·m in 10 N·m steps.
Or on a test run of the vehicle, turn fully the steering wheel (lock condition) and use
M.U.T.-III to forcibly activate the electronic control coupling at 500 N·m. Then drive
the vehicle forward (or back) at about 10 km/h. If the system is normal, tight cornering phenomenon
should occur.
Item 01: 4WD coupling control torque
Q.
Does the electronic control coupling transfer the torque correctly?
Go to Step 5.
Replace the electronic control coupling. Then go to Step 6.
STEP 5. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3)Check if the diagnosis code is set.
Q.
Is the diagnosis code No. C145F set?
Replace 4WD-ECU (Refer to ). Then go to Step
6.
The code may be set because of some severe operational conditions such as a long-time
high speed driving or long hill-climbing in 4WD condition.
STEP 6. Check whether the diagnosis code is reset.
Go to Step 4.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting/CAN
Bus Diagnostics Table 
). On completion, go to Step 2.