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Diagnostic Item 19

DIAGNOSTIC ITEM 19: Diagnose When The Scan Tool Cannot Receive The Data Sent By A/C-ECU [Vehicles With A/C] Or Heater Control Unit [Vehicles Without A/C].

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.


CAN-B Communication Circuit (Part 1):




CAN-B Communication Circuit (Part 2):






FUNCTION
If the scan tool MB991958 cannot communicate with the A/C-ECU [vehicles with A/C] or heater control unit [vehicles without A/C], this diagnosis result will be set.

TROUBLE JUDGMENT CONDITIONS
If a communication flag is not set for the A/C-ECU [vehicles with A/C] or heater control unit [vehicles without A/C], the ETACS-ECU determines that there is a failure.

TROUBLESHOOTING HINTS
- Malfunction of the connector [joint connector (CAN1), A/C-ECU [vehicles with A/C] or heater control unit [vehicles without A/C] connector improperly connected]
- Malfunction of the wiring harness [open circuit between the A/C-ECU [vehicles with A/C] or heater control unit [vehicles without A/C] connector and the joint connector (CAN1), power supply circuit to the A/C-ECU [vehicles with A/C] or heater control unit [vehicles without A/C]]
- Malfunction of the A/C-ECU [vehicles with A/C] or heater control unit [vehicles without A/C]

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe

STEP 1. Check joint connector (CAN1) C-105 and A/C-ECU connector C-22 [vehicles with A/C] or heater control unit connector C-53 [vehicles without A/C] for loose, corroded or damaged terminals, or terminals pushed back in the connector.

CAUTION: The strand end of the twisted wire should be within 10 cm (4 inches) from the connector.

Q: Are joint connector (CAN1) C-105 and A/C-ECU connector C-22 [vehicles with A/C] or heater control unit connector C-53 [vehicles without A/C] in good condition?

YES : Go to Step 2.

NO : Repair the damaged parts.

STEP 2. Check the wiring harness between joint connector (CAN1) C-105 and A/C-ECU connector C-22 [vehicles with A/C] or heater control unit connector C-53 [vehicles without A/C] for open circuit.

CAUTION: Strictly observe the specified wiring harness repair procedure.

1. Disconnect joint connector (CAN1) C-105 and A/C-ECU connector C-22 [vehicles with A/C] or heater control unit connector C-53 [vehicles without A/C], and check the wiring harness.







2. Check the wiring harness between joint connector (CAN1) C-105 (terminal 1) and A/C-ECU connector C-22 [vehicles with A/C] or heater control unit connector C-53 [vehicles without A/C] (terminal 11)

OK: Continuity exists (2 ohms or less)







3. Check the wiring harness between joint connector (CAN1) C-105 (terminal 12) and A/C-ECU connector C-22 [vehicles with A/C] or heater control unit connector C-53 [vehicles without A/C] (terminal 12)

OK: Continuity exists (2 ohms or less)

Q: Is the wiring harness between joint connector (CAN1) C-105 and A/C-ECU connector C-22 [vehicles with A/C] or heater control unit connector C-53 [vehicles without A/C] in good condition?

YES : Check the power supply circuit of the A/C-ECU [vehicles with A/C] or heater control unit [vehicles without A/C]. Refer to Diagnosis Symptom Chart [vehicles with A/C] or Symptom Chart [vehicles without A/C].

NO : Repair the wiring harness between joint connector (CAN1) C-105 and A/C-ECU connector C-22 [vehicles with A/C] or heater control unit connector C-53 [vehicles without A/C].
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