Electronic Control

DTC U0100: Engine 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 U0100 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 engine-ECU.

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 the DTC No. U0001.

^ IG1 power supply voltage: 10 V or more
^ Chassis No. signal, throttle angle signal, or engine speed signal cannot be received.

TROUBLESHOOTING HINTS

Current trouble
^ Wiring harness or connector failure in the CAN bus lines between the engine ECU and AWD-ECU
^ Engine ECU malfunction
^ AWD-ECU malfunction

Past trouble
^ Refer to "How to treat past trouble" for proceeding the diagnostics. Diagnose mainly wiring harness or connector failure in the CAN bus lines between the engine ECU and AWD-ECU, and malfunction in the power supply system for the engine ECU.

NOTE: For 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. You can narrow down the possible cause of the trouble by referring to the DTC, which is set regarding the CAN communication-linked ECUs.

DIAGNOSIS
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A

STEP 1. Scan tool MB991958 CAN bus diagnostics
Use scan tool MB991958 to diagnose the CAN bus lines.

Q:Is the check result normal?
YES: Go to Step 2.
NO: Repair the CAN bus line. 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 engine control system.

Q:Is the DTC set?
YES: Troubleshoot the engine control system.
NO: 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.

^ Meter
U0100: Engine CAN time-out DTC
^ ETACS
U0100: Engine CAN time-out DTC
^ A/C
U0100: Engine CAN time-out DTC

Q:Is the DTC set?
YES: Go to Step 4.
NO: Go to Step 5.

STEP 4. Check whether the DTC is reset.
(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.

Q:Is the DTC No. U0100 set?
YES: Replace the engine control module. Then go to Step 6.
NO: A poor connection, open circuit or other intermittent malfunction in the CAN bus lines between the engine ECU and the AWD-ECU is suspected. Then go to Step 5

STEP 5. Check whether the DTC is reset.

Q:Is the DTC No. U0100 set?
YES: Replace AWD-ECU. Then go to Step 6.
NO: A poor connection, open circuit or other intermittent malfunction in the CAN bus lines between the engine ECU and AWD-ECU is suspected.

STEP 6. Check whether the DTC is reset.

Q:Is the DTC No. U0100 set?
YES: Diagnose again from Step 1.
NO: This diagnosis is complete.