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DTC U0401 Engine (CAN message)
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
  • If DTC No.U0401 is set in ASC-ECU, always diagnose the CAN bus line. If there is any fault in the CAN bus lines, an incorrect DTC may be set. In this case, the set DTC is not highly reliable.
  • Before replacing the ECU, ensure that the communication circuit is normal.
 
 
OPERATION
Engine-related signals are sent or received to and from between ASC-ECU and ECM via CAN bus lines.
 
 
 
DTC SET CONDITIONS
This DTC is set when the ECM malfunction has been detected.
 
 
 
TROUBLESHOOTING HINTS
  • Malfunction of engine system
  • Malfunction of ECM
  • Malfunction of ASC-ECU
  • External noise interference
 
 
 
 
DIAGNOSIS
STEP 1. Scan tool (M.U.T.-III) CAN bus diagnostics
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III). Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(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.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ). On completion, go to Step 5.
 
STEP 2. Scan tool (M.U.T.-III) DTC
Use scan tool (M.U.T.-III) to check that any DTC other than the code No.U0401 is set in ASC-ECU.
Is the DTC set?
Troubleshoot the relevant DTC, and then go to Step 5.
Go to Step 3.
 
STEP 3. Scan tool (M.U.T.-III) other system DTC
Use scan tool (M.U.T.-III) to check that the DTC is set in the engine control module.
Is the DTC set?
Troubleshoot the relevant DTC, and then go to Step 5.
Go to Step 4.
 
STEP 4. Check whether the DTC is set again.
Erase the DTC.
Is DTC No.U0401 set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ), and then go to Step 5.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
 
STEP 5. Check whether the DTC is set again.
Erase the DTC.
Is DTC No.U0401 set?
Return to Step 1.
This diagnosis is complete.