Code No.P1901: CAN signal time-out (Engine-ECU)


caution
  • If diagnosis code P1901 is set in the A/T-ECU, always diagnose the CAN main bus line. 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.

DIAGNOSIS CODE SET CONDITIONS


Current trouble
  • Connector(s) or wiring harness in the CAN bus lines between the engine-ECU and the A/T-ECU, the power supply system to the engine-ECU, the engine-ECU itself, or the A/T-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 A/T-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 - How to Cope with Intermittent Malfunctions ). 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, Explanation about the M.U.T.-III CAN Bus Diagnostics ).

PROBABLE CAUSES



  • Damaged wiring harness or connector
  • Malfunction of the engine-ECU
  • Malfunction of the A/T-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, Diagnosis - Can Bus Diagnostic Chart ), 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 output?
YES : Diagnose the diesel fuel system (Refer to GROUP 13A, Troubleshooting ).
Go to Step 3.

STEP 3. M.U.T.-III diagnosis code
Reconfirm whether the diagnosis codes are output from A/T-ECU.
(1)Erase the diagnosis code.
(2)Turn the ignition switch to ON position.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code output?
Go to Step 4.
Intermittent malfunction in CAN bus line between engine-ECU and A/T-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, re-check the A/T diagnosis code output.

Q. Is the diagnosis code output?
Replace the A/T-ECU.
The check is end.