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Diagnostic Item 28: Diagnose when the scan tool (M.U.T.-IIISE) cannot receive the data sent by A/C controller assembly.
 
 
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.-IIISE) cannot receive the sent data from the A/C controller assembly" when the scan tool (M.U.T.-IIISE) checks the periodically sent data from each ECU and cannot receive the A/C controller assembly data only.
 
 
TROUBLE JUDGMENT CONDITIONS
The scan tool (M.U.T.-IIISE) judges the trouble when the periodically sent data from A/C controller assembly cannot be received.
 
 
PROBABLE CAUSES
  • Damaged harness wires and connectors
  • Power supply circuit malfunction of the A/C controller assembly
  • Malfunction of the heater controller assembly
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Connector check: joint connector (CAN5) and A/C controller assembly connector
cautionThe strand end of the twist wire should be within 10 cm (3.9 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 (CAN5) and A/C controller assembly 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 (CAN5) and the A/C controller assembly 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 (CAN5) terminal No.8 and A/C controller assembly connector terminal No.32
OK: The resistance should be 2 ohms or less
(5) Continuity between joint connector (CAN5) terminal No.19 and A/C controller assembly connector terminal No.31
OK: The resistance should be 2 ohms or less
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<All the resistances measure 2 ohms or less> Go to Step 3.
: <Either or all of the resistances measure more than 2 ohms> Repair the wiring harness between joint connector (CAN5) and the A/C controller assembly connector.
 
STEP 3. Resistance measurement at A/C controller assembly connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the A/C controller assembly, and measure at the equipment side.
(2) Resistance between A/C controller assembly connector terminal Nos.32 and 31
OK: 1 kΩ or more
Is the check result normal?
Power supply to the A/C controller assembly may be suspected. Diagnose the A/C. Refer to GROUP 55 - Troubleshooting .
Replace the A/C controller assembly.