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.
Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
OPERATION
The 4WD-ECU calculates the electronic control coupling temperature by the information
of the electronic control coupling control amount, outside temperate, etc. If it is detected
that the electronic control coupling temperature becomes extremely high, the high fluid temperature
warning is displayed on the warning indicator.
DIAGNOSIS CODE SET CONDITION
This diagnosis code is set when the abnormality below is detected:
The control is suspended to protect the electronic control coupling.
PROBABLE CAUSES
Electronic control coupling protection control status
Severe driving
Electronic control coupling failure (clutch slippage, etc.)
Outside temperature signal failure
Wheel speed signal failure
Engine-related failure (engine speed signal failure)
Ignition off time signal failure
DIAGNOSIS PROCEDURE
STEP 1. Check whether the diagnosis code is reset.
(1)To release the electronic control coupling (Centre) protection control, leave the
vehicle for 15 minutes or longer after the high fluid temperature warning on the warning indicator
disappears.
(2)Erase the diagnosis code.
(3)Carry out the test drive.
note
Do not carry out the severe test drive.
(4)Check if the diagnosis code is set.
Q.
Is diagnosis code No.C1621 set?
Go to Step 2.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunction ).
STEP 2. M.U.T.-III CAN bus diagnostics.
Use M.U.T.-III to perform the CAN bus diagnosis.
Q.
Is the check result normal?
Go to Step 4.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting ).
After repairing the CAN bus line, go to Step 3.
STEP 3. Check whether the diagnosis code is reset.
Q.
Is diagnosis code No.C1621 set?
Go to Step 4.
This diagnosis is complete.
STEP 4. M.U.T.-III data list
Check the following data list (Refer to ).
Item No.12: Engine speed
Q.
Is the check result normal?
Go to Step 5.
Perform the troubleshooting for the engine (Refer to GROUP 13A - Troubleshooting <4B1>, GROUP
13C -Troubleshooting <4J1>, GROUP 13D -Troubleshooting <4N1>).
STEP 5. M.U.T.-III data list
Check the following data list (Refer to ).
Item No.18: FL Wheel speed sensor
Item No.19: FR Wheel speed sensor
Item No.20: RL Wheel speed sensor
Item No.21: RR Wheel speed sensor
Q.
Is the check result normal?
Go to Step 6.
Perform the ABS diagnosis code (Refer to GROUP 35B - Troubleshooting ) <Vehicles
with ABS> or the ASC diagnosis code (Refer to GROUP 35C - Troubleshooting ) <Vehicles
with ASC>.
STEP 6. M.U.T.-III data list
Check the following data list (Refer to ).
Item No.34: Ambient temperature (CAN input)
Item No.35: Ignition off time (CAN input)
Q.
Is the check result normal?
Go to Step 7.
Perform the troubleshooting for the ETACS (Refer to GROUP 54A - ETACS,
Troubleshooting ).
STEP 7. Check of the electronic control coupling
Refer to .
Q.
Is the check result normal?
Go to Step 8.
Replace the electronic control coupling (Refer to ).
STEP 8. Check whether the diagnosis code is reset.
(1)To release the electronic control coupling protection control, leave the vehicle
for 15 minutes or longer after the high fluid temperature warning on the warning indicator disappears.
(2)Erase the diagnosis code.
(3)Carry out the test drive.
note
Do not carry out the severe test drive.
(4)Check if the diagnosis code is set.
Q.
Is diagnosis code No.C1621 set?
Replace the 4WD-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunction ).
Go to Step 2.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunction 
).