Diagnostic Item 22
DIAGNOSTIC ITEM 22: Diagnose the lines between CAN main bus line and the A/C-ECU.CAUTION: When servicing a CAN bus line, ground yourself by touching a metal object such as an unpainted water pipe. If you fail to do so, a component connected to the CAN bus line may be damaged.
Part 1:
Part 2:
TROUBLE JUDGMENT
If the M.U.T.-III cannot received signals from the A/C-ECU, CAN bus line connector(s) are broken or an open circuit has occurred.
COMMENTS ON TROUBLE SYMPTOM
The wiring harness wire or connectors may have loose, corroded, or damage terminals, or terminals pushed back in the connector, or the A/C-ECU may be defective.
TROUBLESHOOTING HINTS
- The wiring harness or connectors may have loose, corroded, or damage terminals, or terminals pushed back in the connector
- The A/C-ECU may be defective
DIAGNOSIS
Required Special Tool:
- MB991223: Harness Set
STEP 1. Check joint connector (3) C-02 and A/C-ECU connector C-10
CAUTION: The strand end of the twisted wire should be within 10 cm (4 inches) from the connector.
Check the joint connector at the wiring harness side for loose, corroded or damaged terminals, or terminals pushed back in the connector, and also check the short pin behind the connector for corrosion, deformation and delamination.
Q: Are joint connector (3) C-02 and A/C-ECU connector C-10
YES: Go to Step 2.
NO: Repair the damaged parts. Replace the joint connector as necessary.
STEP 2. Check the CAN bus lines between joint connector (3) and the A/C-ECU. Measure the resistance between joint connector (3) C-02 and A/C-ECU connector C-10
CAUTION: A digital multimeter should be used.
CAUTION: The test wiring harness should be used.
1. Disconnect joint connector (3) C-02 and A/C-ECU connector C-10
2. Turn the ignition switch to the "LOCK" (OFF) position.
CAUTION: Disconnect the negative battery terminal.
3. Disconnect the negative battery terminal.
4. Measure the resistance between joint connector (3) terminal 17 and A/C-ECU connector terminal 6
OK: 2 ohms or less
5. Measure the resistance between joint connector (3) terminal 6 and A/C-ECU connector terminal 5
OK: 2 ohms or less
CAUTION: Strictly observe the specified wiring harness repair procedure.
Q: Do all the resistances measure 2 ohms or less?
YES: If all the resistances measure 2 ohms or less, power supply to the A/C-ECU may be suspected. Diagnose the air conditioning system. Refer to Heater and A/C, Manual A/C diagnosis.
NO: If either of the resistances measures more than 2 ohms or all the resistances measure more than 2 ohms, repair the wiring harness between joint connector (3) and the A/C-ECU connector.