Manual Air Conditioning
DTC U0154: Occupant classification-ECU Time-out
CAUTION:
If DTC U0154 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 occupant classification-ECU via the CAN bus lines. If any of the air conditioning control-related signals from the occupant classification-ECU cannot be received, the diagnostic trouble code U0154 is stored.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
- Connector(s) or wiring harness in the CAN bus lines between the Occupant classification-ECU and the A/C-ECU, the power supply system to the Occupant classification-ECU, the Occupant classification-ECU itself, or the A/C-ECU may be defective.
Past trouble
- If DTC U0154 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 Occupant classification-ECU, and the power supply system to the Occupant classification-ECU. 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 On-Board Diagnostics).
TROUBLESHOOTING HINTS
- Malfunction of the Occupant classification-ECU
- 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 Occupant classification-ECU diagnostic trouble code.
Check whether an Occupant classification-ECU DTCs are set or not.
(1)Turn the ignition switch to the "ON" position.
(2)Check for Occupant classification-ECU DTCs.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
Q. Is the check result satisfactory?
YES Go to Step 3.
NO Diagnose the Occupant classification-ECU Occupant Classification).
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 Occupant classification-ECU 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 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 lines between the SRS-ECU and the A/C-ECU Harness Connector Inspection.)
NO Replace the Occupant classification-ECU. 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 lines between the SRS-ECU and the A/C-ECU Harness Connector Inspection.)
NO Replace the A/C-ECU. On completion, check that the DTC is not reset.