Code No. U1120: Engine (CAN message)

caution

If diagnosis code U1120 is set in the transfer-ECU, always diagnose the CAN main bus line.
Whenever the ECU is replaced, ensure that the communication circuit is normal.

DIAGNOSIS CODE SET CONDITIONS

Current trouble

The engine-ECU, or the transfer-ECU may be defective.

Past trouble

Carry out diagnosis with particular emphasis on connector(s) or wiring harness in the CAN bus lines between the engine-ECU and the transfer-ECU, and the power supply system to the engine-ECU. For diagnosis procedures, refer to "How to cope with past trouble" (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points

note

For a past trouble, you may not find it by the M.U.T.-III CAN bus diagnostics even if there is any failure in CAN bus lines. In this case, refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points

. and check the CAN bus lines. You can narrow down the possible cause of the trouble by referring to the diagnosis code, which is set regarding the CAN communication-linked ECUs (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow

PROBABLE CAUSES

Damaged wiring harness or connector
Malfunction of the transfer-ECU
Malfunction of the engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics

Using M.U.T.-III, perform CAN bus line diagnosis.

Q. Is the check result normal?

	Go to Step 2.

	Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ). and then go to Step 4.

STEP 2. M.U.T.-III other system diagnosis codes

Check whether the diesel fuel system diagnosis codes are set or not.

Q. Is the diagnosis code set?

	YES : Diagnose the diesel fuel system (Refer to GROUP 13C - Troubleshooting <4N1>).

	Go to Step 3.

STEP 3. M.U.T.-III diagnosis code

Reconfirm whether the diagnosis codes are set in the transfer-ECU.

(1)Erase the diagnosis code.

(2)Check if the diagnosis code is set.

Q. Is the diagnosis code set?

	Go to Step 4.

	Intermittent malfunction in CAN bus line between engine-ECU and transfer-ECU (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).

STEP 4. Replace the engine-ECU

After replacing the engine-ECU (Refer to GROUP 13C - Engine-ECU

<4N1>), re-check the transfer-ECU diagnosis code output.

Q. Is the diagnosis code set?

	Replace the transfer-ECU (Refer to ).

	The check is end.