Manual A/C Diagnosis

DTC U1111: Multi-Center Display Unit (Middle Grade Type) Time-out

CAUTION
- If DTC U1111 is set in the A/C-ECU, diagnose the CAN main bus line.
- Whenever the ECU is replaced, ensure that the communication circuit is normal.

NOTE: *: When the DTC relating to the CAN communication error are output, make sure of the vehicle equipment. When the vehicle is not equipped with the system the A/C-ECU communicates to, the DTC is always output. This is not abnormal.

TROUBLE JUDGMENT
The A/C-ECU receives signals from the multi-center display unit (middle grade type). If the ECU cannot receive the signal related to the multi-center display unit, DTC U1111 will be set.

TECHNICAL DESCRIPTION (COMMENT)

Current trouble
- Connector(s) or wiring harness in the CAN bus lines between the A/C-ECU and the middle-grade multi-center display unit, the power supply system to the display unit, the display unit itself, or the A/C-ECU may be defective.

Past trouble
- When DTC U1111 is set as a past trouble, carry out diagnosis with particular emphasis on connector(s) or wiring harness in the CAN bus lines between the A/C-ECU and the middle-grade multi-center display unit, the power supply system to the display unit. If the connectors and wiring are normal, and obviously the ECU or the middle-grade multi-center display is the cause of the trouble, replace the ECU or the middle-grade multi-center display. If in doubt, do not replace the ECU or the display unit.

NOTE: For a past trouble, you cannot find it by the scan too CAN bus diagnostics even if there is a failure in the CAN bus lines. In this case check the CAN bus lines. 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 Explanation about the scan too CAN bus diagnostics). Explanation About the Scan Tool (M.U.T.-III) CAN Bus Diagnostics

TROUBLESHOOTING HINTS
- Malfunction of middle-grade multi-center display unit
- Malfunction of the A/C-ECU
- Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:
- MB991223:: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.

CAUTION: To 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).







1. Connect scan tool MB991958 to the data link connector.
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.

Q: Is the CAN bus line found to be normal?

YES : Go to Step 2.

NO : Repair the CAN bus line.

STEP 2. Using scan tool MB991958, read the powertrain control module diagnostic trouble code.







Check that the middle-grade multi-center display unit sets a DTC.

1. Turn the ignition switch to the "ON" position.
2. Check for the DTC related to the middle-grade multi-center display unit.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES : Go to Step 3.

NO : Refer to Middle-grade multi-center display unit - Diagnosis. Diagnostic Trouble Code Descriptions

STEP 3. Using scan tool MB991958, check for any diagnostic trouble code.







Check if a DTC, which relates to CAN communication-linked systems below, is set.

- ETACS-ECU
DTC indicating a time-out error of middle-grade multi-center display unit
1. Turn the ignition switch to the "ON" position.
2. Check for a DTC related to the relevant system.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES : Go to Step 5.

NO : Go to Step 4.

STEP 4. Recheck for diagnostic trouble code.







Check again if the DTC is set.

1. Turn the ignition switch to the "ON" position.
2. Check if the DTC is set.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES : A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the middle-grade multi-center display unit and the A/C-ECU.

NO : Replace the middle-grade multi-center display unit. On completion, check that the DTC is not reset.

STEP 5. Recheck for diagnostic trouble code.







Check again if the DTC is set.

1. Turn the ignition switch to the "ON" position.
2. Check if the DTC is set.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES : A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the middle-grade multi-center display unit and the A/C-ECU.

NO : Replace the A/C-ECU. On completion, check that the DTC is not reset.