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Diagnostic Item 9: Diagnose when the scan tool cannot receive the data sent by auto A/C controller assembly (A/C-ECU). <Vehicles with automatic A/C>
 
 
cautionWhen servicing a CAN bus line, ground yourself by touching a metal object such as an unpainted water pipe. If you fail to do, a component connected to the CAN bus line may be broken.
 
 
FUNCTION
The diagnostic result demonstrates that "the scan tool (M.U.T.-III) cannot receive the sent data from the auto A/C controller assembly (A/C-ECU)" when the scan tool (M.U.T.-III) checks the periodically sent data from each ECU and cannot receive the auto A/C controller assembly (A/C-ECU) data only.
 
 
TROUBLE JUDGMENT CONDITIONS
scan tool (M.U.T.-III) judges the trouble when the periodically sent data from auto A/C controller assembly (A/C-ECU) cannot be received.
 
 
PROBABLE CAUSES
  • Damaged harness wires and connectors
  • Power supply circuit malfunction of the auto A/C controller assembly (A/C-ECU)
  • Malfunction of the auto A/C controller assembly (A/C-ECU)
 
 
DIAGNOSIS
STEP 1. Connector check: joint connector (CAN1) and auto A/C controller assembly (A/C-ECU) connector
cautionThe strand end of the twist wire should be within 10 cm (4 inches) from the connector. For details refer to .
When checking the joint connector, ensure that its wiring harness side and its short pins are not damaged.
Is the check result normal?
Go to Step 2.
Repair the defective connector. Replace the joint connector as necessary.
 
STEP 2. Resistance measurement at joint connector (CAN1) and auto A/C controller assembly (A/C-ECU) connector.
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN1) and the auto A/C controller assembly (A/C-ECU) connector, and measure at the wiring harness side.
(2) Turn the ignition switch to the "LOCK" (OFF) position.
(3)
cautionWhen measuring the resistance, disconnect the negative battery terminal. For details refer to .
Ensure that the negative battery terminal is disconnected.
(4) Continuity between joint connector (CAN1) terminal No.7 and auto A/C controller assembly (A/C-ECU) connector terminal No.12
OK: Continuity (2 Ω or less)
(5) Continuity between joint connector (CAN1) terminal No.18 and auto A/C controller assembly (A/C-ECU) connector terminal No.11
OK: Continuity (2 Ω or less)
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<All the resistances measure 2 Ω or less> Power supply to the auto A/C controller assembly (A/C-ECU) may be suspected. Diagnose the automatic A/C. Refer to GROUP 55B - Troubleshooting .
<Either or all of the resistances measure more than 2 Ω> Repair the wiring harness between joint connector (CAN1) and the auto A/C controller assembly (A/C-ECU) connector.