Code No.U1120 Engine-related failure information


caution
  • If the electric power steering-ECU sets 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.
  • Whenever the ECU is replaced, ensure that the communication circuit is normal.


TROUBLE JUDGMENT
The electric power steering-ECU receives engine speed data (crankshaft angle sensor data) from the engine-ECU <M/T> or engine-A-M/T-ECU <Automated manual transmission> through the CAN bus lines. If the ECU receives engine speed data (crankshaft angle sensor data) containing failure information 100 times, diagnosis code U1120 will be set.

COMMENTS ON TROUBLE SYMPTOM
The M.U.T.-III shows a diagnosis code status as active
  • The crankshaft angle sensor system (of the engine-ECU <M/T> or engine-A-M/T-ECU <Automated manual transmission>), or the engine-ECU <M/T>, the engine-A-M/T-ECU <Automated manual transmission> or the electric power steering-ECU may be defective.
The M.U.T.-III shows a diagnosis code status as stored
  • Carry out diagnosis by referring to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to treat past trouble ). Carry out diagnosis with particular emphasis on connector(s) or wiring harness in the CAN bus lines between the engine-ECU <M/T> or engine-A-M/T-ECU <Automated manual transmission> and the electric power steering-ECU.
    note For a The M.U.T.-III shows a diagnosis code status as stored, you can 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-How to Cope with Intermittent Malfunction 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

  • Defective harness wire(s) or connector(s)
  • Malfunction of the engine-ECU <M/T> or engine-A-M/T-ECU <Automated manual transmission>
  • Malfunction of the electric power steering-ECU

DIAGNOSIS PROCEDURE

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

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
(1)Connect M.U.T.-III to the 16-pin diagnosis connector.
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the check result normal?

Go to Step 2.

Repair the CAN bus line (Refer to GROUP 54C - CAN bus line Diagnostic flow ).

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

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Check that an engine control system diagnosis code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is an engine control system diagnosis code set?

Diagnose the engine control system (Refer to GROUP 13A - Troubleshooting - Inspection chart for diagnosis code <134 or 3A9>, GROUP 13B - Troubleshooting - Inspection chart for diagnosis code <135 or 4A9> or GROUP 13C - Troubleshooting - Inspection chart for diagnosis code <4G1>.

Go to Step 3.

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

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Check if a diagnosis code, which relates to CAN communication-linked systems below, is set.

  • Meter
    U1120: Diagnosis code indicating engine control-related failure information
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the diagnosis code set?

Go to Step 4.

Go to Step 5.

STEP 4. Check whether the diagnosis code is reset

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Recheck whether diagnosis code U1120 is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the diagnosis code set?

Replace the engine-ECU <M/T> or engine-A-M/T-ECU <Automated manual transmission> (Refer to GROUP 13A - Engine-ECU <134 or 3A9>, GROUP 13B - Engine-ECU, Engine-A-M/T-ECU <135 or 4A9>, GROUP 13C - Engine-ECU <4G1>).

A poor connection, open circuit or other intermittent malfunction may be present between the engine-ECU <M/T> or the engine-A-M/T-ECU <Automated manual transmission> and the crankshaft angle sensor. Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .

STEP 5. Check whether the diagnosis code is reset

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Recheck whether diagnosis code U1120 is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.
(7)Disconnect M.U.T.-III.

Q. Is the diagnosis code set?

Replace the electric power steering-ECU (Refer to ).

A poor connection, open circuit or other intermittent malfunction may be present between the engine-ECU <M/T> or the engine-A-M/T-ECU <Automated manual transmission> and the crankshaft angle sensor. Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .