When the diagnosis
code No. B1731 is set, be sure to diagnose the CAN bus line.
When replacing the ECU, always check that the communication circuit is normal.
DIAGNOSIS FUNCTION
ETACS-ECU checks if the data from the engine-ECU is received via the CAN bus line. When
ETACS-ECU cannot receive the engine-ECU data, it sets the diagnosis code No. B1731.
JUDGEMENT CRITERIA
ETACS-ECU determines that the abnormality is present, if it cannot receive the data from
the engine-ECU via the CAN bus line when the ignition switch is turned ON.
PROBABLE CAUSES
Malfunction of CAN bus line
Damaged wiring harness and connectors
Malfunction of Engine-ECU
Malfunction of ETACS-ECU
DIAGNOSIS PROCEDURE
STEP 1. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set to ETACS-ECU.
(1)Erase the diagnosis code.
(2)Remove the ignition key from key cylinder and insert it again then turn the ignition
switch from the Lock (OFF) position to the ON position.
(3)On completion, check that the diagnosis code is not reset.
Q.
Is the diagnosis code set?
Go to Step 2.
There is an intermittent malfunction such as poor engaged connector(s) or open
circuit (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 diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 3.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ).
On completion, go to Step 3.
STEP 3. M.U.T.-III other system diagnosis code
Check whether an engine-related diagnosis code is set.
Q.
Is the diagnosis code set?
Perform troubleshooting for the engine (Refer to GROUP 13A - Troubleshooting ).
Go to Step 4.
STEP 4. M.U.T.-III other system diagnosis code
Check if diagnosis code No.U0100 is set to ETACS-ECU.
Q.
Is the diagnosis code set?
Go to Step 6.
Go to Step 5.
STEP 5. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set to ETACS-ECU.
(1)Remove the ignition key from key cylinder and insert it again then turn the ignition
switch from the Lock (OFF) position to the ON position.
(2)Check if the diagnosis code is set.
Q.
Is the diagnosis code set?
Replace ETACS-ECU and register the ID codes (Refer to ).
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points - How to Cope with Intermittent Malfunction ).
STEP 6. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set to ETACS-ECU.
(1)Remove the ignition key from key cylinder and insert it again then turn the ignition
switch from the Lock (OFF) position to the ON position.
(2)Check if the diagnosis code is set.
Q.
Is the diagnosis code set?
Replace the engine-ECU and register the chassis number and key codes [Refer
to GROUP 00 - How to Perform Chassis Number (Chassis No.) Writing ].
There is an intermittent malfunction such as poor engaged connector(s) or open
circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction 
).