Code No.U1406: Accelerator pedal position signal error


caution
  • 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, Trouble code diagnosis ).
  • If diagnosis code U1406 is set in TCL/ASC-ECU, always diagnose the CAN bus line. If there is any fault in the CAN bus lines, an incorrect diagnosis code may be set. In this case, the set diagnosis code is not highly reliable.
  • Before replacing the ECU, ensure that the communication circuit is normal.

DIAGNOSIS CODE SET CONDITIONS
TCL/ASC-ECU receives the engine control system-related signals from the engine-ECU or engine-A-M/T-ECU via the CAN bus lines. If these signals contain information of malfunction, this code is stored.

COMMENTS ON TROUBLE SYMPTOM
Current trouble
  • Wiring harness or connector(s) in the CAN bus lines between TCL/ASC-ECU and engine-ECU or engine-A-M/T-ECU, the power supply circuit to engine-ECU or engine-A-M/T-ECU or TCL/ASC-ECU may have a problem.
Past trouble
  • When the diagnosis code No. U1406 is stored as a past trouble, carry out diagnosis with particular emphasis on failures of wiring harness and connector(s) in the CAN bus lines between TCL/ASC-ECU and engine-ECU or engine-A-M/T-ECU, and the power supply circuit to engine-ECU or engine-A-M/T-ECU. For diagnosis procedures, refer to How to treat past trouble (refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points ).
    note For a past trouble, it is impossible to find any failure in CAN bus lines by the M.U.T.-III CAN bus diagnostics. 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

  • Malfunction of engine-ECU or engine-A-M/T-ECU
  • Malfunction of TCL/ASC-ECU
  • Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis
Use 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 - CAN Bus Diagnosis table ). On completion, go to Step 3.

STEP 2. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No.U1406 set?
Go to Step 3.
This diagnosis is complete.

STEP 3. M.U.T.-III Diagnosis code of other systems
Use M.U.T.-III to check if the diagnosis code is set in the engine-ECU or engine-A-M/T-ECU.

Q. Is the diagnosis code set?
Perform troubleshooting for the relevant diagnosis code.
Replace the engine-ECU or engine-A-M/T-ECU, and then go to Step 4.

STEP 4. Check whether the diagnosis code is reset
Check again if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition switch: "LOCK" (OFF)
(3)Ignition switch: "ON"

Q. Is the diagnosis code No.U1406 set?
Replace the hydraulic unit (integrated with TCL/ASC-ECU) (Refer to ).
This diagnosis is complete.