If the EPS-ECU
sets the diagnosis code No. U1120, diagnose the CAN bus lines. If there is any fault in the
CAN bus lines, an incorrect diagnosis code may be set.
Before replacing ECU, ensure that the communication circuit is normal.
TROUBLE JUDGEMENT
EPS-ECU receives the READY signal from the EV-ECU via CAN bus lines. If the EPS-ECU receives
the READY signal containing failure information twice, the diagnosis code No. U1120 will be
set.
COMMENT ON TROUBLE SYMPTOM
Current trouble
The EV-ECU itself or EPS-ECU itself may be faulty.
Past trouble
Carry out the diagnosis with particular emphasis on the EV-ECU. For diagnosis procedures,
refer to "How to Cope with Historic Trouble" (GROUP 00 - How to Use Troubleshooting/Inspection
Service Points ).
PROBABLE CAUSES
Defective harness wire(s) or connector(s)
Malfunction of the EV-ECU
Malfunction of the EPS-ECU
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnosis
Use the M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines. (Refer to GROUP 54C, Troubleshooting .)
STEP 2. Use M.U.T.-III to confirm a diagnosis code of other systems.
Check if the diagnosis code is set to the EV-ECU.
Q.
Is the diagnosis code set?
Perform the troubleshooting for the EV-ECU (refer to group 54D - EV-ECU - Diagnosis
Code Chart ).
Go to Step 3.
STEP 3. Use M.U.T.-III to confirm a diagnosis code of other systems.
Check if a diagnosis code, which relates to the CAN communication-linked systems below,
is set.
Combination meter
EV system-related CAN communication fail information
Q.
Is the diagnosis code set?
Go to Step 4.
Go to Step 5.
STEP 4. Diagnosis code recheck
Recheck if the diagnosis code is set.
(1)Turn the electric motor switch to the "LOCK" (OFF) → "ON" position.
(2)Start the electric motor unit.
(3)Check if the diagnosis code No. U1120 is set as a current trouble.
Q.
Is the diagnosis code No. U1120 set?
Replace the EV-ECU.
An intermittent malfunction may be present. (Refer to GROUP 00 - How
to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent
Malfunction .)
STEP 5. Diagnosis code recheck
Recheck if the diagnosis code is set.
(1)Turn the electric motor switch to the "LOCK" (OFF) → "ON" position.
(2)Start the electric motor unit.
(3)Check if the diagnosis code No. U1120 is set as a current trouble.
Q.
Is the diagnosis code No. U1120 set?
Replace EPS-ECU.
An intermittent malfunction may be present. (Refer to GROUP 00 - How
to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent
Malfunction .)
). 
Go to Step 2.
Repair the CAN bus lines. (Refer to GROUP 54C, Troubleshooting 