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
EPS-ECU receives vehicle speed signal from the engine-ECU.
FUNCTION
The vehicle speed signal is sent to the EPS-ECU for
motor control.
TROUBLE JUDGEMENT
Check Conditions
The power supply circuit system diagnosis code (No. C1540, C1541) is not set.
The engine circuit system diagnosis code is not set.
Judgement Criterion
If the microcomputer receives abnormal vehicle speed signal from the engine-ECU
consecutively twice, it determines that the vehicle speed calculation system is defective.
Fail Safe, Back Up Function
The EPS-ECU illuminates the electric power steering warning display, and sets the
diagnosis code No. C1564 to limit assist operation.
PROBABLE CAUSES
Malfunction of CAN bus line
Malfunction of the EPS-ECU
Malfunction of the engine-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 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
(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 codes C1564 set?
Go to Step 3
This diagnosis is complete.
STEP 3. M.U.T.-III data list
Check the following service data .
Item No. 08: Vehicle speed
Q.
Is the check result normal?
Go to Step 5
Perform troubleshooting for engine-ECU (Refer to GROUP 13A - Troubleshooting .
Then go to Step 4.
STEP 4. 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 codes C1564 set?
Replace the EPS-ECU (Refer to ). Then go to
Step 5.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunction ).
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.
Go to Step 3
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table 
).
On completion, go to Step 2.