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DTC U1000: OSS CAN timeout
 
 
caution
  • If DTC U1000 is set in the A/C controller assembly (A/C-ECU), diagnose the CAN main bus line.
  • Whenever the ECU is replaced, ensure that the communication circuit is normal.
 
 
DTC SET CONDITION
The A/C controller assembly (A/C-ECU) receives air conditioning control-related signals from the KOS&OSS-ECU via the CAN bus lines. If the ECU cannot receive any of the air conditioning control-related signals from the KOS&OSS-ECU, DTC U1000 will be set.
 
 
 
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
  • Connector(s) or wiring harness in the CAN bus lines between the KOS&OSS-ECU and the A/C controller assembly (A/C-ECU), the power supply system to the KOS&OSS-ECU, the KOS&OSS-ECU itself, or the A/C controller assembly (A/C-ECU) may be defective.
Past trouble
  • Carry out diagnosis with particular emphasis on connector(s) or wiring harness in the CAN bus lines between the A/C controller assembly (A/C-ECU) and the KOS&OSS-ECU, and the power supply system to the KOS&OSS-ECU. For diagnostic procedures, refer to "How to treat past trouble" (Refer to GROUP 00 - How to Treat Past Trouble ).
    noteFor a past trouble, you can not find it by the scan tool (M.U.T.-IIISE) CAN bus diagnostics even if there is any failure in CAN bus lines. In this case, refer to GROUP 00, How to Cope with Intermittent Malfunction 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 (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow ).
    cautionIf the ignition switch is turned to the ON position without starting the engine, DTC U1000 (past trouble) may be set in the A/C controller assembly (A/C-ECU) after three minutes.
 
 
 
TROUBLESHOOTING HINT
  • The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
  • Malfunction of the KOS&OSS-ECU
  • Malfunction of the A/C controller assembly (A/C-ECU)
 
 
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ."
(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.
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C, Troubleshooting ).
 
STEP 2. Using scan tool (M.U.T.-IIISE), check other system DTC.
Check if DTC is set in the KOS&OSS-ECU.
Is the DTC set?
Diagnose the KOS&OSS-ECU. Refer to GROUP 42B, Troubleshooting .
Go to Step 3.
 
STEP 3. Using scan tool (M.U.T.-IIISE), check other system DTC.
Check if a DTC, which relates to CAN communication-linked systems below, is set.
  • Combination meter
    U1000: OSS CAN timeout
Is the DTC set?
Go to Step 4.
Go to Step 5.
 
STEP 4. Check whether the DTC is set again.
Recheck if the DTC is set.
(1) Erase the DTC.
(2) Ignition switch: "LOCK" (OFF) to "ON"
(3) Check if the DTC is set.
Is the DTC set?
Replace the KOS&OSS-ECU.
A poor connection, open circuit or other intermittent malfunction in the CAN bus line between the KOS&OSS-ECU and the A/C controller assembly (A/C-ECU) (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
 
STEP 5. Check whether the DTC is set again.
Recheck if the DTC is set.
(1) Erase the DTC.
(2) Ignition switch: "LOCK" (OFF) to "ON"
(3) Check if the DTC is set.
Is the DTC set?
Replace the A/C controller assembly (A/C-ECU).
A poor connection, open circuit or other intermittent malfunction in the CAN bus line between the KOS&OSS-ECU and the A/C controller assembly (A/C-ECU) (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).