Automatic Air Conditioning
DTC U0155: Combination meter Time-out
CAUTION:
If DTC U0155 is set in the A/C-ECU, diagnose the CAN main bus line.
CAUTION:
Whenever the ECU is replaced, ensure that the communication circuit is normal.
TROUBLE JUDGMENT
The A/C-ECU receives the air conditioning control-related signals from the combination meter via the CAN bus lines. If any of the air conditioning control-related signals from the combination meter cannot be received, the diagnostic trouble code U0155 is stored.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
- Connector(s) or wiring harness in the CAN bus lines between the combination meter and the A/C-ECU, the power supply system to the combination meter, the combination meter itself, or the A/C-ECU may be defective.
Past trouble
- If DTC U0155 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) in the CAN bus line between the A/C-ECU and the combination meter, and the power supply system to the combination meter. If the connectors and wiring are normal, and obviously the ECU is the cause of the trouble, replace the ECU. If in doubt, do not replace the ECU.
NOTE:
For a past trouble, you cannot find it by the scan tool CAN bus diagnostics even if there is a failure in CAN bus lines. In this case, refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions How to Cope With Intermittent Malfunctions ) and 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 Initial Inspection and Diagnostic Overview ).
TROUBLESHOOTING HINTS
- Malfunction of the combination meter
- 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
(1)
CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
Connect scan tool MB991958. Refer to "How to connect the Scan Tool (M.U.T.-III) Reading and Clearing Diagnostic Trouble Codes."
(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 CAN Bus Diagnostics Chart).
STEP 2. Using scan tool MB991958 read the combination meter diagnostic trouble code.
Check whether a combination meter DTCs are set or not.
(1)Turn the ignition switch to the "ON" position.
(2)Check for combination meter DTCs.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
Q. Is the DTC set?
YES Diagnose the combination meter Combination Meter).
NO Go to Step 3.
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 related to the combination meter system
(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 DTC set?
YES Go to Step 4.
NO Go to Step 5.
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 DTC set?
YES Replace the combination meter. On completion, check that the DTC is not reset.
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions.)
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 DTC set?
YES Replace the A/C-ECU. On completion, check that the DTC is not reset.
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions.)