Manual Air Conditioning
DTC U1000: OSS-ECU Time-out
CAUTION:
If DTC U1000 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 OSS-ECU via the CAN bus lines. If any of the air conditioning control-related signals from the OSS-ECU cannot be received, diagnostic trouble code U1000 is stored.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
- Connector(s) or wiring harness in the CAN bus lines between the OSS-ECU and the A/C-ECU, the power supply system to the OSS-ECU, the OSS-ECU itself, or the A/C-ECU may be defective.
Past trouble
- If DTC U1000 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 OSS-ECU, and the power supply system to the OSS-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, 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 CAN Bus Line Diagnostics Flow ).
TROUBLESHOOTING HINTS
- Malfunction of the OSS-ECU
- Malfunction of the A/C-ECU
- Damaged wiring harness or connectors
DIAGNOSIS
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 OSS-ECU diagnostic trouble code.
Check whether an OSS-ECU DTCs are set or not.
(1)Turn the ignition switch to the "ON" position.
(2)Check for OSS-ECU DTCs.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
Q. Is the DTC set?
YES Go to Step 3.
NO Diagnose the OSS-ECU Wireless Control Module (WCM)).
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 OSS-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 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 OSS-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.)
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.)