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DTC U0101: T/M CAN time-out
 
 
caution
  • If more than three minutes elapse after the ignition switch is turned ON without starting engine, AWD-ECU may set DTC U0101 as past trouble.
  • If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, always diagnose the CAN bus lines.
  • Before replacing the ECU, ensure that the communication circuit is normal.
 
 
OPERATION
AWD-ECU temporarily limits the AWD functions if it has not received the signal from the transmission control module.
 
 
DTC SET CONDITIONS
If the following conditions are met when the system is in operation (always), AWD-ECU gradually switches the control from AWD to AWD AUTO, flashes the AWD/LOCK indicators alternately, and sets DTC U0101.
  • IG1 power supply voltage: 10 V or more
  • Chassis No. signal, throttle angle signal, or transmission speed signal cannot be received.
 
 
TROUBLESHOOTING HINTS
Current trouble
  • Wiring harness or connector failure in the CAN bus lines between the transmission control module and AWD-ECU
  • transmission control module malfunction
  • AWD-ECU malfunction
Past trouble
  • Refer to "How to treat past trouble" (GROUP 00 - How to Use Troubleshooting/How to Treat Past Trouble ) for proceeding the diagnostics. Diagnose mainly wiring harness or connector failure in the CAN bus lines between the transmission control module and AWD-ECU, and malfunction in the power supply system for the transmission control module.
    noteFor a past trouble, you cannot find it by the scan tool MB991958 CAN bus diagnostics even if there is any failure in CAN bus lines. In this case, check the CAN bus lines in the same manner as How to cope with intermittent malfunction (refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunction ). You can narrow down the possible cause of the trouble by referring to the DTC, which is set regarding the CAN communication-linked ECUs. (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow .)
 
 
DIAGNOSIS
STEP 1. Scan tool MB991958 CAN bus diagnostics
Use scan tool MB991958 to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting/CAN Bus Diagnostics Table ). Then go to Step 2.
 
STEP 2. Scan tool MB991958 DTC of other systems
Check that the bus-off error DTC is set in the transmission control system.
Is the DTC set?
Troubleshoot the transmission control system (Refer to GROUP 23A - Troubleshooting/DTC Chart ).
Go to Step 3.
 
STEP 3. Scan tool MB991958 DTC of other systems
Check if a DTC, which relates to the CAN communication-linked systems below, is set.
  • Combination meter
    U0101: transmission CAN time-out DTC
  • ETACS
    U0101: transmission CAN time-out DTC
Is the DTC set?
Go to Step 4.
Go to Step 5.
 
STEP 4. Check whether the DTC is set again.
(1) Erase the DTC.
(2) Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3) Check if the DTC is set.
Is DTC U0101 set?
Replace the transmission control module (Refer to GROUP 23A - transmission Control Module ). Then go to Step 6.
A poor connection, open circuit or other intermittent malfunction in the CAN bus lines between the transmission control module and the AWD-ECU is suspected (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ). Then go to Step 5.
 
STEP 5. Check whether the DTC is set again.
Is DTC U0101 set?
Replace AWD-ECU (Refer to ). Then go to Step 6 .
A poor connection, open circuit or other intermittent malfunction in the CAN bus lines between the transmission control module and AWD-ECU is suspected (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
 
STEP 6. Check whether the DTC is set again.
Is DTC U0101 set?
Diagnose again from Step 1.
This diagnosis is complete.