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DTC U1900: Loss of MCU message (K-line)
 
 
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 ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.
 
 
DTC SET CONDITIONS
The PHEV-ECU sets DTC U1900 when it cannot communicate via K lines.
 
 
 
PROBABLE CAUSES
  • K-line between FEMCU and PHEV-ECU fails.
  • Malfunction of the FEMCU.
  • Malfunction of the PHEV-ECU.
 
 
 
 
DIAGNOSIS
Required Special Tools
  • MB991223: Wiring harness set
  • MB992006: Extra fine probe
STEP 1. Check the signal line for open circuit and short to ground circuit (PHEV-ECU and the FEMCU).
Check the wiring harness between brake PHEV-ECU connector (terminal KLN1) and the FEMCU connector (terminal KLN1).
Is the check result normal?
Go to Step 2.
Repair the connector or wiring harness.
 
STEP 2. Using scan tool (M.U.T.-IIISE), check whether the other DTC is set.
Check if DTC U1920 is set in the FEMCU (Refer to GROUP 54Db - Diagnostic Function ).
Is the DTC set?
Carry out troubleshooting for the DTC U1920 (Refer to GROUP 54Db - Trouble Shooting, Diagnostic Trouble Code Procedures ).
Go to Step 3.
 
STEP 3. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Recheck the DTC.
(1) Erase the DTC.
(2) Turn off the power supply mode of the electric motor switch.
(3) Turn on the power supply mode of the electric motor switch.
(4) Check the DTC
Is the DTC set?
Replace the PHEV-ECU (Refer to ). Then go to Step 4.
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
 
STEP 4. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Recheck the DTC.
(1) Erase the DTC.
(2) Turn off the power supply mode of the electric motor switch.
(3) Turn on the power supply mode of the electric motor switch.
(4) Check the DTC.
Is the DTC set?
Replace the power drive unit (FEMCU) (Refer to GROUP 54Db - Power Drive Unit Removal and Installation ).
The procedure is complete.